<2>A 45-year-old man presents to a physician with back pain and facial pain. Physical examination demonstrates coarse facial features and kyphosis. Laboratory examination is remarkable for elevated alkaline phosphatase . X-ray studies demonstrate skull thickening with narrowing of foramina, and bowing of the femur and tibia. Bone biopsy reveals a mosaic pattern of bone spicules with prominent osteoid seams. Which of the following neoplasms occurs at an increased frequency in patients with this disorder? A. Astrocytoma B. Hodgkin's lymphoma C. Meningioma D. Non-Hodgkin's lymphoma E. Osteosarcoma Answer
<3> Which of the labeled structures is responsible for the secretion of renin? A. A B. B C. C D. D E. E Answer
<4>A 42-year-old African-American man sustains severe injuries in an automobile accident and is admitted to the intensive care unit. Examination of a peripheral blood smear on the 3rd day of admission reveals helmet cells, schistocytes, and decreased platelets. Which of the following is most strongly suggested by these findings? A. Autoimmune hemolysis B. Disseminated intravascular coagulation (DIC) C. Hereditary spherocytosis D. Megaloblastic anemia E. Sickle cell anemia Answer
<5>A 12-month-old child is diagnosed with an atrial septal defect. What is the most common cause of such a congenital heart malformation? A. Failure of formation of the septum primum B. Failure of formation of the septum secundum C. Incomplete adhesion between the septum primum and septum secundum D. Malformation of the membranous interventricular septum E. Malformation of the muscular interventricular septum Answer
<6>A 72-year-old man with prostate cancer is treated with leuprolide. What is the mechanism of action of this drug? A. It inhibits 5a-reductase B. It is a competitive antagonist at androgen receptors C. It is a competitive inhibitor of LH D. It is a synthetic analog of GnRH E. It is a testosterone agonist Answer
<7>An XX genotypic infant is born with ambiguous genitalia. Laboratory examination reveals hypoglycemia, hyperkalemia, and salt wasting. S erum 17-OH progesterone is markedly increased. Which of the following is the most likely diagnosis? A. 5-alpha-reductase deficiency B. 11-beta-hydroxylase deficiency C. 17-alpha-hydroxylase deficiency D. 21-hydroxylase deficiency E. Complete androgen resistance Answer
<8>A 57-year-old fisherman with a history of alcoholism is hospitalized in Gulfport, Mississippi with a 1-day history of severe, watery diarrhea after eating several raw oysters. He is badly dehydrated on admission, and within 12 hours, he becomes severely hypotensive and dies. Which of the following pathogens is the most likely cause of this man's death? A. Citrobacter diversus B. Enterotoxigenic E. coli C. Providencia stuartii D. Vibrio cholerae E. Vibrio vulnificus Answer
<9>An Hispanic male is referred to the dermatology clinic of a major medical center. On physical examination, the man has several disfiguring lesions on his face and there is loss of cutaneous sensation to fine touch, pain, and temperature. An acid-fast organism is observed in scrapings from a skin lesion. Which of the following organisms is the most likely cause of this patient's disease? A. Bartonella henselae B. Listeria monocytogenes C. Mycobacterium avium-intracellulare D. Mycobacterium leprae E. Nocardia asteroides Answer
<10>Microscopic examination of a section of a normal young adult ovary reveals large numbers of unusually large cells surrounded by a single layer of flat epithelial cells. In which phase of the cell cycle are these cells arrested? A. Diplotene stage of the 1st meiotic division B. Diplotene stage of the 2nd meiotic division C. Metaphase stage of mitosis D. Prophase stage of mitosis E. Prophase stage of the 2nd meiotic division Answer
<11>A 3-year-old child is seen by a pediatrician because he has developed multiple isolated lesions on his face and neck. Physical examination reveals many lesions up to 4 cm in diameter with golden crusts, while in other sites small blisters and weeping areas are seen. Which of the following is the most likely diagnosis? A. Aphthous ulcers B. Erysipelas C. Herpes simplex I D. Impetigo E. Measles Answer
<12>A 2-year-old-boy is brought to the pediatrician by his mother because he has had several episodes of rectal bleeding. Evaluation with a technetium-99m perfusion scan reveals a 3-cm ileal outpouching located 60 cm from the ileocecal valve. This structure likely contains which of the following types of ectopic tissue? A. Duodenal B. Esophageal C. Gastric D. Hepatic E. Jejunal Answer
<13>A 19-year-old college student presents to the student health clinic complaining of weakness, malaise, and a chronic cough. He has a fever of 100 degrees F and a dry cough; no sputum can be obtained for laboratory analysis, so a bronchial lavage is performed and the washings are submitted to the laboratory. The laboratory reports that the organism is "slow-growing." Serodiagnosis reveals Strep MG agglutinins in the patient's serum. Which of the following organisms is the most likely cause of this student's illness? A. Klebsiella pneumoniae B. Mycoplasma pneumoniae C. Parainfluenza virus D. Respiratory syncytial virus E. Streptococcus pneumoniae Answer
<14>A 52-year-old male is brought into the emergency room by his wife because he has been complaining of a severe headache. Physical exam reveals ptosis of the right eyelid with the right eye facing down and out. There is a fixed and dilated right pupil with an inability to accommodate. Subarachnoid blood appears on noncontrast CT scan. Magnetic resonance angiography (MRA) would be expected to reveal an aneurysm of which of the following vessels? A. Anterior cerebral artery B. Anterior choroidal artery C. Anterior communicating artery D. Middle cerebral artery E. Ophthalmic artery F. Posterior communicating artery G. Posterior inferior cerebellar artery Answer
<15>A 24-year-old graduate student presents to a physician with complaints of severe muscle cramps and weakness with even mild exercise. Muscle biopsy demonstrates glycogen accumulation, but hepatic biopsy is unremarkable. Which of the following is the most likely diagnosis? A. Hartnup's disease B. Krabbe's disease C. McArdle's disease D. Niemann-Pick disease E. Von Gierke's disease Answer
<16>A baby is born with a flat facial profile, prominent epicanthal folds, and simian crease. She vomits when fed, and upper GI studies demonstrate a "double bubble" in the upper abdomen. Which of the following cardiovascular abnormalities might this child also have? A. Atrial septal defect B. Berry aneurysm C. Coarctation of the aorta D. Endocardial cushion defect E. Tetralogy of Fallot Answer
<17>An asymptomatic, 24-year-old African-American woman in her second trimester of pregnancy has the following laboratory findings: Based on the laboratory data, which of the following tests is necessary for fur ther evaluation of this patient? A. Creatinine clearance B. Oral glucose tolerance test C. Serum ferritin D. Sickle cell preparation E. No further study is necessary Answer
<18>Endometrial biopsy demonstrates a thick endometrium with long, coiled glands lined by a columnar epithelium with prominent cytoplasmic vacuoles adjacent to the gland lumen. Earlier in the menstrual cycle, the glands were much smaller and were lined with cells that did not have vacuoles. Which of the following hormones is primarily responsible for inducing this change in appearance? A. Aldosterone B. Cortisol C. Estrogen D. Progesterone E. Thyroxine Answer
<19>A 28-year-old man discovers a mass in his neck while buttoning his shirt collar. Physical examination reveals a 2 cm mass in one thyroid lobe, which is "cold" on scintiscan. Aspiration of the nodule demonstrates small "solid balls" of neoplastic follicular cells. Careful examination of these tissue balls reveals that they contain microscopic blood vessels and fibrous stroma in their centers. Which of the following is the most likely diagnosis? A. Follicular carcinoma B. Hashimoto's disease C. Medullary carcinoma D. Papillary carcinoma E. Thyroid adenoma Answer
<20>Nissl bodies correspond to which of the following cytoplasmic organelles? A. Golgi apparatus B. Mitochondria C. Nucleoli D. Rough endoplasmic reticulum E. Smooth endoplasmic reticulum Answer
<21>A 40-year-old man with sleep apnea participates in a sleep study. During his evaluation, normal sawtooth waves are observed on his EEG tracing. This pattern is associated with which period of sleep? A. REM B. Stage 1 C. Stage 2 D. Stage 3 E. Stage 4 Answer
<22>A United Nations representative from a poor African country has an influenza-like illness that resolves in a few days. Less than a week later, however, he develops muscle pain, spasms, and sensory disturbances. Two days after this, flaccid paralysis occurs. Which of the following is most likely to be immediately life-threatening in this patient? A. Acute renal failure B. Bowel paralysis C. Fulminant liver failure D. Gastrointestinal bleeding E. Respiratory paralysis Answer
<23>What is the normal myeloid to erythroid ratio in bone marrow? A. 1:1 B. 1:3 C. 1:10 D. 3:1 E. 10:1 Answer
<24>A 45-year-old male complains of fatigue and increased frequency of urination. Questioning reveals that he is somewhat confused. Physical examination reveals a 5'10", 240 lb. individual whose fat is centrally distributed. Urine is positive for glucose, but negative for ketones. A blood sample drawn from this patient is likely to exhibit which of the following compared to that of a normal individual? A. Decreased concentration of C-peptide B. Decreased pH C. Increased antibodies against islet cell proteins D. Increased concentration of b-hydroxybutyrate E. Increased osmolarity Answer
<25>At which of the following ages does fetal movement first occur? A. 1 month B. 2 months C. 4 months D. 6 months E. 7 months Answer
<26>A child with retinoblastoma is found to have a 13q14 deletion. The Rb gene, which resides at this locus, produces which kind of tumor-associated protein? A. Cell cycle regulator B. Growth factor C. Growth factor-binding protein D. Growth factor receptor E. Transcription activator Answer
<27>A 29-year-old woman is involved in an automobile accident, and is taken to the emergency room by paramedics. X-rays reveal a fracture of her pelvis. During the healing of the pelvic fracture, the obturator nerve becomes entrapped in the bone callus. Compression of this nerve by the growing bone may result in weakness of which of the following muscles? A. Adductor magnus B. Biceps femoris C. Rectus femoris D. Sartorius E. Vastus medialis Answer
<28>An African child develops massive unilateral enlargement of his lower face in the vicinity of the mandible. Biopsy demonstrates sheets of medium-sized blast cells with admixed larger macrophages. This type of tumor has been associated with which of the following? A. Epstein-Barr virus and t(8;14) B. Hepatitis B and t(9;22) C. Herpesvirus and CD5 D. Human immunodeficiency virus and CD4 E. Human papillomavirus and t(2;5) Answer
<29>A 57-year-old man presents for a routine physical. His blood pressure is 161/98 mm Hg. The patient's only complaint is that over the past several months he has had difficulty urinating. His urine stream is intermittent, and he has recently begun experiencing nocturia and profound urinary urgency. Digital rectal exam reveals diffuse enlargement of the prostate. Which of the following agents would be most likely to effectively treat the man's urinary tract symptoms as well as his hypertension? A. Finasteride B. Guanfacine C. Hydralazine D. Labetalol E. Terazosin Answer
<30>A 54-year-old male with extensive, severe atherosclerosis sustains a thrombotic occlusion of the celiac trunk. The organs that receive their blood supply from this artery continue to function normally. Anastomoses between which of the following pairs of arteries would explain this phenomenon? A. Left gastric artery and right gastric artery B. Left gastroepiploic artery and right gastroepiploic artery C. Proper hepatic artery and gastroduodenal artery D. Right colic artery and middle colic artery E. Superior pancreaticoduodenal artery and inferior pancreaticoduodenal artery Answer
<31>A cardiovascular pharmacologist is researching the effects of new compounds on arteriolar resistance. Drug X maximally increases vascular resistance by 50% at a dose of 20 mg/mL. Drug Y maximally increases vascular resistance by 75% at a dose of 40 mg/mL. Which of the following conclusions can the researcher draw from this experiment? A. Drug X has a smaller volume of distribution than Drug Y B. Drug X has a shorter half-life than Drug Y C. Drug X is less efficacious than Drug Y D. Drug X is less potent than Drug Y E. Drug X has a lower LD50 than Drug Y Answer
<32>A 74-year-old woman, in otherwise good health, tripped and injured her right leg 2 days previously and has been bedridden since the accident . Two hours ago, she became delirious. On physical examination, her temperature is 99 F, blood pressure is 120/70 mm Hg, heart rate is 110, and respiratory rate is 32. Pulse oximetry shows an oxygen saturation of 80%, and a chest x-ray film is normal. Which of the following is the most likely diagnosis? A. Acute cerebral hemorrhage B. Acute cerebral infarction C. Myocardial infarction D. Pulmonary infarction E. Pulmonary thromboembolism Answer
<33>A 25-year-old pregnant woman complains to her obstetrician of dysuria. Microscopic examination of the urine demonstrates many gram-negative rods, many neutrophils, and a few WBC casts. Which of the following is the specific significance of the presence of WBC casts? A. One or both kidneys are involved in the infection B. One or both ureters are involved in the infection C. The bladder is involved in the infection D. The urethra is involved in the infection E. The uterus is involved in the infection Answer
<34>A 45-year-old female with a long history of progressive myopia develops sudden patchy loss of vision in her right eye. She is very alarmed and rushes to her family doctor. Funduscopic examination reveals a large retinal detachment in the right eye. The retina in the left eye is normal. When the pupillary light reflex is tested by shining a light in the right eye, the physician would likely note A. constriction of the right pupil and constriction of the left B. constriction of the right pupil and dilatation of the left C. dilatation of the right pupil and constriction of the left D. dilatation of the right pupil and dilatation of the left E. no reaction of the right pupil and constriction of the left Answer
<35>Physical examination of a young boy reveals discharge of urine from the umbilicus. The physician concludes that the urachus has failed to fuse. Which of the following structures is the normal adult remnant of the fused urachus? A. Lateral umbilical fold B. Medial umbilical fold C. Medial umbilical ligament D. Median umbilical fold E. Median umbilical ligament Answer
<36> In this section of a healing bone fracture, which of the following best describes the cell at the arrow? A. Apoptotic cell B. Bone-lining macrophage C. Dividing osteoblast D. Necrotic cell E. Typical osteoblast Answer
<37>A retarded 45-year-old man living in Mexico becomes ill with pneumonia and his family brings him across the border to the United States. He succumbs to his illness and an autopsy is performed. Neuropathological examination of his brain reveals neuritic plaques and neurofibrillary tangles. Which of the following was the most likely cause of this man's retardation? A. Down's syndrome B. Edwards' syndrome C. Fragile X syndrome D. Patau syndrome E. Supernumerary Y syndrome Answer
<38>A 59-year-old woman presents with complaints of "feeling tired." She also admits to frequent headaches, which occur on one side and are throbbing. Physical examination is remarkable for a temperature of 100°F (37.8°C) and tenderness over both temples. Laboratory tests reveal a slightly decreased hematocrit and an elevated erythrocyte sedimentation rate. This patient should be treated aggressively to prevent the development of A. blindness B. deafness C. loss of tactile sensation D. loss of the ability to speak E. paralysis Answer
<39>A newborn baby has projectile vomiting shortly after each feeding. It is determined that there is obstruction of the digestive tract as a result of an annular pancreas. Annular pancreas is a result of an abnormality in which of the following processes? A. Rotation of the dorsal pancreatic bud around the first part of the duodenum B. Rotation of the dorsal pancreatic bud around the second part of the duodenum C. Rotation of the dorsal pancreatic bud around the third part of the duodenum D. Rotation of the ventral pancreatic bud around the first part of the duodenum E. Rotation of the ventral pancreatic bud around the second part of the duodenum Answer
<40>A debilitated 72-year-old woman develops dry cough, fever, headache, and muscular pains. She treats herself with aspirin and ampicillin without any improvement. Her children take her to a local hospital, where chest x-ray films reveal scattered opacities, suggestive of interstitial infiltration. Laboratory investigations demonstrate the presence of cold agglutinins. She is treated with erythromycin, and her symptoms rapidly improve. Which of the following is the most likely etiologic agent of this patient's condition? A. Influenza virus B. Mycoplasma pneumoniae C. Pneumocystis carinii D. Respiratory syncytial virus E. Streptococcus pneumoniae Answer
<41>Which of the following hormones is most important in initiating gall bladder contraction? A. Cholecystokinin (CCK) B. Gastric inhibitory peptide (GIP) C. Gastrin D. Secretin E. Vasoactive intestinal polypeptide (VIP) Answer
>42>A patient complains to her family physician that "When it's time to go to work, I just can't seem to get out of the house. I have a lot of windows, and I need to check them all three times. Then, I can never be sure the door is locked, so I check it 3 times. I've been late for work a few times, but this is the only way I can be sure the house is safe. Sometimes I think I'm going to go crazy." Which of the following is the most likely diagnosis? A. Adjustment disorder with anxiety B. Agoraphobia without history of panic disorder C. Generalized anxiety disorder D. Obsessive compulsive disorder E. Panic disorder with agoraphobia Answer
<43>A 32-year-old male, infected with HIV, is diagnosed with Hodgkin's lymphoma. If the patient's CD4 count is 505/mm3, which of the following agents would be suitable for the treatment of this patient's lymphoma without further compromising his immune system? A. Busulfan B. Cisplatin C. Cyclophosphamide D. Paclitaxel E. Vincristine Answer
<44>A 62-year-old Type 2 diabetic patient presents with complaints of malaise, myalgias, respiratory distress, and increased somnolence. If laboratory examination reveals an anion gap of 26 mmol/L, HCO3- of 17 mmol/L and an arterial blood pH of 7.27, the patient is most likely receiving A. glyburide B. metformin C. repaglinide D. miglitol E. troglitazone Answer
<45>A 24-year-old delivery driver is involved in an accident and sustains a wide abrasion over his left elbow. The abrasion results in the total loss of epidermis over a large area of his left arm, but one month later, the abrasion has healed, with regrowth of the epidermis. Which of the following mechanisms accounts for the restoration of the epidermis over the abraded area? A. Growth of epidermis from hair follicles and sweat glands in the dermis B. Migration of endothelial cells from newly grown capillaries C. Transformation of dermal fibroblasts into epidermal cells D. Transformation of macrophages into epidermal cells E. Transformation of melanocytes into epidermal cells Answer
<46> The diagram above shows spirographic tracings of forced expirations from two different individuals. Trace X was obtained from a person with healthy lungs. Which of the following is most likely represented by trace Y? A. Asthma B. Bronchospasm C. Emphysema D. Interstitial fibrosis E. Old age Answer
<47>A patient has multiple, pearly papules on the face. Biopsy shows a malignant tumor. Which of the following features would most likely be seen on microscopic examination? A. Cytoplasmic viral inclusions B. Keratin "pearls" C. Melanin D. Palisading nuclei E. S-100 positivity Answer
<48>A neonate develops marked unconjugated hyperbilirubinemia. No hemolysis can be demonstrated and other liver function tests are normal. There is no bilirubin found in the urine. This infant's condition continues to deteriorate and he dies at 2 weeks of age. To which of the following conditions did the infant most likely succumb? A. Crigler-Najjar syndrome, Type I B. Crigler-Najjar syndrome, Type II C. Dubin-Johnson syndrome D. Gilbert's syndrome E. Rotor syndrome Answer
<49>A 41-year-old woman presents with chronic widespread musculoskeletal pain, fatigue, and frequent headaches. She states that her musculoskeletal pain improves slightly with exercise. On examination, painful trigger points are produced by palpitation of the trapezius and lateral epicondyle of the elbow. If objective signs of inflammation are absent and laboratory studies are normal, this patient would most likely be responsive to which of the following drugs? A. Amitriptyline B. Cefaclor C. Naproxen D. Oxycodone E. Prednisone Answer
<50>A 29-year-old medical student developed a positive PPD (purified protein derivative) test. She was started on isoniazid (INH) and rifampin prophylaxis. Three months into her therapy, she began to experience muscle fasciculations and convulsions. Administration of which of the following vitamins might have prevented these symptoms? A. Niacin B. Pyridoxine C. Riboflavin D. Thiamine E. Vitamin C Answer
Answers
1The correct answer is C. A small percentage of patients (5% to 10%) develop a nonoliguric form of acute renal failure when treated with aminoglycosides such as gentamicin. Gentamicin can accumulate in the kidney to produce a delayed form of acute renal failure resulting in an elevation of the serum creatinine level. The nonoliguric form of renal failure, seen in this patient, is the typical presentation for gentamicin nephrotoxicity. Acute glomerulonephritis (choice A) is typically associated with hypertension and the appearance of an active urinary sediment containing casts and red blood cells. Cephalothin (choice B) is a first-generation cephalosporin commonly used in the treatment of severe infection of the genitourinary tract, gastrointestinal tract, and respiratory tract, as well as skin infections. This antibiotic can produce an acute interstitial nephritis; however, the patient's presentation is consistent with gentamicin nephrotoxicity. Interstitial nephritis is commonly associated with the development of acute renal failure, fever, rash, and eosinophilia. Renal artery occlusion (choice D) is commonly caused by thrombosis or embolism. The clinical features of acute renal artery occlusion are hematuria, flank pain, fever, nausea, elevated LDH, elevated SGOT and acute renal failure. Since the patient has normal vital signs and no history of hypotension, a diagnosis of sepsis (choice E) is unlikely.
2The correct answer is E. The phrase "mosaic pattern" of newly formed woven bone is a specific tip-off for Paget's disease of bone, and is not seen in other bone conditions. The clinical and radiologic presentation are typical; an increased hat size may also be a clue. In its early stages, Paget's disease is characterized by osteolysis, producing patchwork areas of bone resorption with bizarre, large osteoclasts. In the middle stage of the disease, secondary osteoblastic activity compensates with new bone formation, producing the mosaic pattern. In late Paget's, the bones are dense and osteosclerotic. Paget's disease is suspected to be related to prior viral infection, but the cause remains mysterious. Complications include myelophthisic anemia, high output cardiac failure, pain secondary to nerve compression, deformities secondary to skeletal changes, and in about 1% of patients, osteosarcoma or other sarcoma, typically involving the jaw, pelvis, or femur. An increased incidence of astrocytomas (choice A) is associated with tuberous sclerosis. Hodgkin's lymphoma (choice B) is usually a disease of young adults, although older patients may have the lymphocyte-depleted form. Meningiomas (choice C) are mostly benign tumors that affect adults, especially females. There may be an association with breast cancer, possibly related to high estrogen states. Non-Hodgkin's lymphoma (choice D) is more common in AIDS and other immunodeficiency states, although the incidence in the immunocompetent is increasing.
3The correct answer is C. This question required that you know two pieces of information: (1) renin is secreted from the juxtaglomerular (JG) cells; and (2) the location of the JG cells in a picture that includes both the glomerulus and the juxtaglomerular apparatus. Remember that renin is responsible for converting angiotensinogen to angiotensin I, which is subsequently converted to angiotensin II in the lungs by an important enzyme appropriately called angiotensin-converting enzyme. Angiotensin II helps preserve blood pressure both by its potent vasoconstrictor properties and by its ability to stimulate aldosterone secretion from the adrenal cortex. The label for choice A points to the glomerular basement membrane. The label for choice B points to the epithelium of Bowman's capsule. The label for choice D points to the macula densa cells, which are thought to sense sodium concentration in the distal convoluted tubule. The label for choice E points to the Polkissen cells. Their function is unknown.
4The correct answer is B. The findings suggest disseminated intravascular coagulation (DIC), which is a feared complication of many other disorders, such as obstetrical catastrophes, metastatic cancer, massive trauma, and bacterial sepsis. The basic defect in DIC is a coagulopathy characterized by bleeding from mucosal surfaces, thrombocytopenia, prolonged PT and PTT, decreased fibrinogen level, and elevated fibrin split products. Helmet cells and schistocytes (fragmented red blood cells) are seen on peripheral blood smear. Autoimmune hemolysis (choice A) and hereditary spherocytosis (choice C) would be characterized by spherocytes in the peripheral smear. Macro-ovalocytes and hypersegmented neutrophils can be seen in megaloblastic anemia (choice D). Sickle cells are seen in sickle cell anemia (choice E).
5The correct answer is C. The most common form of atrial septal defect is located near the foramen ovale (not to be confused with a patent foramen ovale, which is of little or no hemodynamic significance). They result from incomplete adhesion between the septum primum and the septum secundum during development. Atrial septal defects less commonly result from failures of formation of the septum primum (choice A) and septum secundum (choice B). Malformations of the interventricular septum (choices D and E) cause ventricular septal defects rather than atrial septal defects.
6The correct answer is D. Leuprolide is a GnRH analog. Given long-term in a continuous fashion, it will inhibit FSH and LH release, thereby decreasing testosterone production and exacting a chemical castration in men. It can be used in the treatment of prostate cancer, polycystic ovary syndrome, uterine fibroids, and endometriosis. Inhibition of 5a-reductase (choice A) is the mechanism of action of finasteride. It thereby inhibits the production of dihydrotestosterone. It is used in the treatment of benign prostatic hyperplasia (BPH). Flutamide is another drug used in the treatment of prostate cancer. It is a competitive antagonist at androgen receptors (choice B). Since LH activates interstitial cells to secrete testosterone, a synthetic analog of LH (choice C) would not be appropriate treatment for prostatic cancer. The same goes for a testosterone analog (choice E). Here is a brief chart that will aid you in remembering the actions of these similar sounding drugs: Drug Action Indication Leuprolide GnRh analog Prostate CA Flutamide Competitive androgen antagonist Prostate CA Finasteride 5a-reductase inhibitor BPH Remember, "loo"prolide and "floo"tamide are both used for prostate cancer. Finasteride is used for BPH.
7The correct answer is D. 21-hydroxylase deficiency is the most common form of congenital adrenal hyperplasia. The simple virilizing variant (without salt wasting) is most common, but with severe 21-hydroxylase deficiency, virilization and salt wasting occur. The infant described above exhibits salt wasting and hyperkalemia because aldosterone secretion is diminished by the enzyme deficiency. The hypoglycemia is due to cortisol deficiency. Because cortisol secretion is diminished in congenital adrenal hyperplasia, ACTH secretion from the anterior pituitary is increased due to loss of negative feedback inhibition. The high levels of ACTH are responsible for the adrenal hyperplasia and the increased secretion of the adrenal androgens, dehydroepiandrosterone and androstenedione, which are responsible for the virilization of the external genitalia. 17-OH progesterone is the steroid precursor just proximal to 21-hydroxylase and is also increased because of the excessive drive to the adrenal cortex by ACTH. 5-alpha-reductase deficiency (choice A) in male fetuses will produce normal differentiation of the internal reproductive tracts, but the external genitalia will be feminized. This is because testosterone needs to be converted to dihydrotestosterone (by 5-alpha-reductase) in the external genitalia and the prostate for normal differentiation into the male phenotype. 11-beta-hydroxylase deficiency (choice B) is another form of congenital adrenal hyperplasia. It is characterized by salt retention due to excessive secretion by the inner zones of the adrenal cortex of the weak mineralocorticoid, deoxycorticosterone. Again, the excessive drive to the adrenal cortex is due to increased ACTH resulting from diminished negative feedback suppression by cortisol. The adrenal also secretes excessive androgens and virilization occurs in female fetuses. 17-alpha-hydroxylase deficiency (choice C) is another from of congenital adrenal hyperplasia that is accompanied by salt retention. The high levels of ACTH drive the adrenal cortex to secrete increased amounts of deoxycorticosterone and corticosterone, both of which have weak mineralocorticoid activity. Without the ability to 17-alpha-hydroxylate progesterone or pregnenolone, steroid-secreting cells cannot produce sex steroids. When 17-alpha-hydroxylase deficiency is present in the adrenal cortex, it is also present in the gonads. Hence, whether it occurs in a male or female fetus, sex steroid production will be diminished. Female fetuses will develop normal reproductive tracts and genitalia since these structures are programmed in utero to "automatically" become female. Male fetuses, however, will have their reproductive tracts and genitalia feminized. Complete androgen resistance (choice E) results in feminization of affected male fetuses. It is characterized by an XY genotypic male with phenotypically female external genitalia and a vagina that ends as a blind sac.
8The correct answer is E. Vibrio vulnificus is an extremely invasive organism, producing a septicemia in patients after eating raw shellfish, or causing wound infections, cellulitis, fasciitis, and myositis after exposure to seawater or after cleaning shellfish. Patients at high risk for septicemia include those with liver disease, congestive heart failure, diabetes mellitus, renal failure, hemochromatosis, and immunosuppression. Citrobacter diversus (choice A) produces neonatal meningitis and can be frequently cultured from the umbilicus. Enterotoxigenic E. coli (choice B) produces the classic traveler's diarrhea. The toxin is ingested in water and salads. The incubation period is approximately 12 hours. The diarrhea is non-inflammatory and treatment is supportive. Providencia stuartii (choice C) is a gram-negative rod related to Proteus. It is a common cause of nosocomial bacteremia in nursing home patients with chronic catheterization. Vibrio cholerae (choice D) produces a non-invasive, non-inflammatory, high-volume secretory diarrhea that is toxin-mediated.
9The correct answer is D. The disease in question is leprosy, or Hansen's disease. A key feature in the description is the fact that the organism is acid-fast. Both of the mycobacteria, M. avium-intracellulare and M. leprae are strongly acid-fast, that is they retain the carbol fuchsin dye in the face of acid-alcohol decolorization. M. leprae has a predilection for the skin and cutaneous nerves, thereby producing the symptoms of depigmentation and anesthetic cutaneous lesions. This loss of peripheral nerve function leads to many of the disfiguring features of the disease; because the patients do not have normal pain sensation, they sustain repeated injuries. In addition, the organism attacks cartilage and causes granuloma formation in the skin, leading to some of the facial disfigurement. Bartonella henselae (choice A) is a very small, gram-negative bacterium that is closely related to the rickettsia, although it is able to be cultured on lifeless media. It is the cause of cat-scratch disease, a local, chronic lymphadenitis most commonly seen in children, and bacillary angiomatosis, a disease seen particularly in AIDS patients. Listeria monocytogenes (choice B) is a ubiquitous microbe that causes disease in over 100 animal species. Although it is best known as an agent of meningitis in the newborn, it is a cause of multiple other diseases. A characteristic feature of these infections is the development of granulomas at the site of the infection. The organism is not acid-fast and has no particular predilection for skin or nervous tissues. M. avium-intracellulare (choice C) causes tuberculosis-like pulmonary disease in the immunosuppressed. Nocardia asteroides (choice E) primarily produces pulmonary infections in humans. The organism is consider to be "weakly" acid-fast, meaning that if the amount of HCl used in the decolorization step is reduced, the organisms will retain the carbolfuchsin primary stain.
10The correct answer is A. The cells described are the primordial eggs, which remain stopped in the diplotene stage of the first meiotic division from before birth until fertilization, a period which may be 40 or more years. Choices B and E are incorrect because the oocytes are stopped in the first, not second meiotic division. Choices C and D are incorrect because the cells described are oocytes and are not in mitosis.
11The correct answer is D. This is impetigo, which is typically seen in preschool children with poor hygiene, particularly in the summer in warm climates. The characteristic lesion has a large golden crust. Most cases are caused by Staphylococcus aureus; Streptococcus pyogenes is occasionally implicated. Impetigo is highly infectious, and mini-epidemics can occur in daycare settings. The initial treatment is typically with penicillins and topical preparations. Methicillin-resistant strains are presently rare in this setting, but can occur. Aphthous ulcers (choice A), commonly known as "canker sores," are painful, shallow ulcers of the oral cavity. Erysipelas (choice B) is a different type of skin infection, often caused by Streptococcus pyogenes (also sometimes others including Staphylococcus), and is characterized by large erythematous patches. Herpes simplex I (choice C) causes tiny oral and perioral vesicles, but not large golden crusts. Measles (choice E) causes a blotchy erythematous rash.
12The correct answer is C. This little boy has a Meckel's diverticulum, an ileal outpocketing typically located within 50-75 cm of the ileocecal valve. It is a congenital anomaly resulting from the persistence of the vitelline (omphalomesenteric) duct. Approximately half cause ulceration, inflammation, and gastrointestinal bleeding due to the presence of ectopic acid-secreting gastric epithelium. Pancreatic tissue may sometimes occur in these diverticula as well. Note that this is the most common type of congenital gastrointestinal anomaly. Something else to keep in mind: A favorite question attendings ask on the wards is the rule of 2's associated with Meckel's diverticulum: it occurs in about 2% of children, occurs within approximately 2 feet of the ileocecal valve, contains 2 types of ectopic mucosa (gastric and pancreatic), and its symptoms usually occur by age 2. All of the other answer choices have no relationship to Meckel's diverticulum.
13The correct answer is B. The patient has primary atypical pneumonia caused by Mycoplasma pneumoniae. This organism is fastidious and difficult to culture in the laboratory, however serodiagnosis can be most helpful. Patients typically produce one or two heterophile antibodies during the course of the infection; one agglutinates human O+ RBCs in the cold (the cold hemagglutinin) while the other causes the agglutination of a strain of Streptococcus salivarius termed strain MG (the Strep MG agglutinins). Klebsiella pneumoniae (choice A) is readily cultured on routine laboratory media and characteristically produces pneumonia with blood clots in the sputum (red currant jelly sputum), which may be indicative of pulmonary abscess development. Parainfluenza viruses (choice C) cause croup, which is characterized by a dry, "barking" cough. It is more of a tracheitis, bronchitis, and bronchiolitis than a pneumonitis. No heterophile antibodies are produced in these patients. Respiratory syncytial virus (choice D) causes an atypical pneumonitis in infants. It is usually diagnosed by the observation of syncytial masses in respiratory secretions. Cold hemagglutinins and Strep MG agglutinins are absent. Streptococcus pneumoniae (choice E) is the number one cause of pneumonia in adults. It also causes septicemia and meningitis in the elderly. The patient has a classical acute pneumonia with a productive cough, high fever with chills, leukocytosis, tachycardia, rapid respirations and other signs of serious respiratory disease. A vaccine, composed of the capsular carbohydrate of 23 serotypes of this organism, is routinely given to individuals over the age of 60, as well as to individuals with splenic abnormalities (e.g., sickle cell disease) who are at increased risk for pneumococcal sepsis.
14The correct answer is F. Aneurysm of the posterior communicating artery is the second most common aneurysm of the circle of Willis (anterior communicating artery is most common) and can result in third cranial nerve palsy (paralysis). The oculomotor nerve (CN III) innervates the levator palpebrae muscle. CN III paralysis would therefore result in ptosis (drooping of the upper eyelid). CN III also innervates all of the extraocular muscles, except for the superior oblique (CN IV) and the lateral rectus muscles (CNVI). Thus, CN III palsy would result in unopposed action of the superior oblique and lateral rectus muscles, causing the affected eye to look down and out. CN III also supplies parasympathetic innervation to the sphincter muscle of the iris (which constricts the pupil) and to the ciliary muscle. Interruption of this pathway leads to a dilated and fixed pupil and to paralysis of accommodation. Note that this question teaches you about another Boards-favorite pathology: subarachnoid hemorrhage (SAH). (In this case, it was due to rupture of a posterior communicating artery aneurysm). A classic clue to the diagnosis is a patient presenting with "the worst headache of their life." When you are presented a case of sudden severe headache, SAH should rank highly on your differential diagnosis list. The anterior cerebral artery (choice A) supplies the medial surface of the cerebral hemisphere, from the frontal pole to the parieto-occipital sulcus. Occlusion may produce hypesthesia and paresis of the contralateral lower extremity. The anterior choroidal artery (choice B) arises from the internal carotid artery and is not part of the circle of Willis. It perfuses the lateral ventricular choroid plexus, the hippocampus, parts of the globus pallidus and posterior limb of the internal capsule. The anterior communicating artery (choice C) connects the two anterior cerebral arteries. It is the most common site of aneurysm in the circle of Willis and may cause aphasia, abulia (impaired initiative), and hemiparesis. The middle cerebral artery (choice D) supplies the lateral convexity of the cerebral hemisphere, including Broca's and Wernicke's speech areas and the face and arm areas of the motor and sensory cortices. It also gives rise to the lateral striate arteries, which supply the internal capsule, caudate, putamen, and globus pallidus. The middle cerebral artery is the most common site of stroke. The ophthalmic artery (choice E) enters the orbit with the optic nerve (CN II) and gives rise to the central artery of the retina. Occlusion results in blindness. The posterior inferior cerebellar artery (choice G) supplies the dorsolateral medulla and the inferior surface of the cerebellar vermis. Occlusion may result in Wallenberg's syndrome: cerebellar ataxia, hypotonia, loss of pain and temperature sensation of the ipsilateral face, absence of corneal reflex ipsilaterally, contralateral loss of pain and temperature sensation in the limbs and trunk, nystagmus, ipsilateral Horner's syndrome, dysphagia, and dysphonia.
15The correct answer is C. A variety of glycogen storage diseases exist, corresponding to defects in different enzymes in glycogen metabolism; most of these involve the liver. McArdle's disease (Type V glycogen storage disease), due to a defect in muscle phosphorylase, is restricted to skeletal muscle. The presentation described in the question stem is typical. Many affected individuals also experience myoglobinuria. Definitive diagnosis is based on demonstration of myophosphorylase deficiency. Hartnup's disease (choice A) is a disorder of amino acid transport. Krabbe's disease (choice B) is a lysosomal storage disease. Niemann-Pick disease (choice D) is a lysosomal storage disease. Von Gierke's disease (choice E) is a glycogen storage disease with prominent involvement of liver, intestine, and kidney.
16The correct answer is D. The disease is Down syndrome (trisomy 21). In addition to mental retardation and the characteristic physical findings described in the question stem, duodenal atresia is fairly common, as evidenced by the "double bubble" sign on x-ray. These children are also likely to have various cardiac anomalies; endocardial cushion defect is the most common. Atrial septal defect (choice A) is one of the most common genetic defects in the general population, but is less common than endocardial cushion defect in patients with Down syndrome. Berry aneurysms (choice B), also known as saccular aneurysms, are typically located in the circle of Willis on the ventral surface of the brain. They occur more frequently in patients with adult polycystic disease. Rupture can produce subarachnoid hemorrhage. Coarctation of the aorta (choice C) occurs more commonly in females with a 45, XO genotype (Turner syndrome). Tetralogy of Fallot (choice E) is the most common cause of early cyanosis, consisting of a ventricular septal defect, right ventricular outflow tract obstruction, an overriding aorta, and right ventricular hypertrophy.
17The correct answer is E. All of the laboratory data in this pregnant woman are normal, hence no further study is necessary. In a normal pregnancy, both the plasma volume and RBC mass are increased with a greater increase in the plasma volume than RBC mass (2:1 ratio). This has a dilutional effect on many laboratory tests. Increasing plasma volume in pregnancy increases the creatinine clearance (choice A) due to the expected elevation in the glomerular filtration rate (GFR). The reference intervals for serum blood urea nitrogen and creatinine are lower than normal, due to the dilutional effect of increased plasma volume and increased clearance of both analytes in the urine caused by the rise in the GFR. The threshold for glucose is reduced in pregnancy, so patients can have a positive dipstick test for glucose in the presence of a normal serum glucose. Therefore, an oral glucose tolerance test (choice B) is not indicated. The hemoglobin (Hb) concentration in pregnancy is normally decreased because of the dilutional effect of increased plasma volume. Since the Hb is normal (for a pregnant woman) in this patient, a serum ferritin (choice C) to rule out iron deficiency is unnecessary. Furthermore, iron deficiency is usually associated with a low MCV (microcytic anemia), and her MCV is normal. Although sickle disease is the most common genetic hemoglobinopathy among African Americans, the patient is not anemic, so there is no reason to order a sickle cell preparation (choice D).
18The correct answer is D. The endometrial phase with small glands is the proliferative phase; the one with large glands with secretory cells is the secretory phase. Estrogen (choice C) is necessary for both phases, but it is the addition of progesterone (choice D), secreted by the corpus luteum after the Graafian follicle ruptures, that triggers the switch from proliferative to secretory endometrium. Glucocorticoids (choice B) and the mineralocorticoid aldosterone (choice A) are secreted by the adrenal glands. They do not produce the endometrial changes described. Thyroxine (choice E) is secreted by the thyroid gland, and is unrelated to the observed morphologic changes in the endometrium.
19The correct answer is D. The distinctive cell balls described are broken-off papillary clusters, and are considered pathognomic for papillary carcinoma of the thyroid. This is the most common form of thyroid carcinoma. It tends to present in the 3rd to 5th decade and shows a modest female predominance. Despite its propensity for local lymphatic intrusion (which may cause multifocality of tumor in the thyroid or cervical lymph node metastases), the tumor generally has an excellent prognosis with 90% 20-year survival. Follicular carcinoma (choice A) is characterized by follicular cells and colloid on aspiration, and cannot be reliably distinguished from thyroid adenoma. Distinctive features of Hashimoto's disease (choice B) on aspiration are lymphocytes, plasma cells, and macrophages. The most distinctive feature of medullary carcinoma (choice C) on aspiration is the presence of amyloid. Thyroid adenoma (choice E) shows follicular cells and colloid on aspiration, and cannot be reliably distinguished from follicular carcinoma.
20The correct answer is D. This is a straightforward question relating to the definition of Nissl bodies. Rough endoplasmic reticulum present in neurons are called Nissl bodies. They stain intensely with basic dyes and are found in the cell body and proximal dendrites, but not in the axon hillock or axon.
21The correct answer is A. Sawtooth waves appearing in bursts are associated with REM sleep. Stage 1 (choice B) is associated with 4-7 Hz theta waves. Stage 2 (choice C) is associated with 12-14 Hz sleep spindles and K-complexes. Stage 3 (choice D) is associated with < 4 Hz, high-amplitude delta waves. Stage 4 (choice E) is characterized by an EEG composed of about 50% delta waves. Note that beta waves (15-18 Hz) occur during periods of more intense mental activity while awake. Alpha waves (8-12 Hz) occur during awake, relaxed states. REM is the stage of sleep that most resembles the awake state on the EEG.
22The correct answer is E. The disease is poliomyelitis. Most infections with poliovirus cause only the influenza-like symptoms, but a small percentage progress to paralytic poliomyelitis. The most common causes of death are aspiration and airway obstruction as a result of bulbar paralysis and paralysis of respiratory muscles. Arrhythmias can also be life-threatening. Acute renal failure (choice A) is usually not seen in poliomyelitis, although the bladder may become paralyzed. Bowel paralysis (choice B) can be seen, but is not usually life-threatening. Fulminant liver failure (choice C) is not a feature of poliomyelitis. Gastrointestinal bleeding (choice D) can be seen in poliomyelitis, but is not usually life-threatening.
23The correct answer is D. The ratio of cells in bone marrow developing along myeloid lines to cells developing along erythroid lines is 3:1. An alternative way to remember the normal marrow composition is that it typically contains about 60% granulocytes and their precursors; 20% erythroid precursors; 10% lymphocytes, monocytes, and their precursors; and 10% unidentified or disintegrating cells. These numbers are worth remembering, because shifts away from normal values may be a subtle clue to marrow abnormalities.
24The correct answer is E. An obese adult with glucosuria, but not ketonuria, likely has type 2 diabetes mellitus. Type 2 diabetes is characterized by insulin resistance resulting in hyperglycemia and increased serum osmolarity. The dehydration associated with osmotic diuresis makes the hyperosmolarity worse. As the osmolarity increases above 330 mOsm/L, the osmotic loss of water from neurons is sufficient to produce coma. In nonketotic, hyperosmolar coma, blood glucose values can range from 800 to 2,400 mg/dL and produce serum osmolarities of 330-440 mOsm/L. Since type 2 diabetes is due to insulin resistance, plasma levels of insulin are usually normal to increased. Because b cells secrete insulin and C-peptide in a 1:1 ratio, plasma concentration of C-peptide would also be normal to increased (not decreased, choice A) in type 2 diabetes. Even small amounts of insulin are sufficient to prevent ketosis. In type 2 diabetes there is enough insulin effect to prevent significant lipolysis and subsequent formation of excess ketone bodies. Hence, acidosis (choice B) is not typically associated with this disorder. Since b-hydroxybutyrate is a ketone body, its concentration in plasma is not likely to be increased (choice D). While there is a significant autoimmune component to type 1 diabetes, type 2 diabetes is not associated with increased circulating antibodies (choice C) against b cell proteins such as glutamic acid decarboxylase.
25The correct answer is B. Neuromuscular development is sufficient to allow fetal movement in the eighth week of life. Other features of week 8 include the first appearance of a thin skin, a head as large as the rest of the body, forward-looking eyes, appearance of digits on the hands and feet, appearance of testes and ovaries (but not distinguishable external genitalia), and a crown-rump length of approximately 30 mm. By the end of the eighth week, nearly all adult structures have at least begun to develop, and the fetus "looks like a baby".
26The correct answer is A. The Rb gene is an example of a tumor suppressor gene. Tumor suppressor genes encode proteins that downregulate cell growth; consequently, their deletion leads to the development of cells with a growth advantage over normal cells. Even if you know nothing about the Rb protein, choice A is still the only logical answer because it is the only example of a protein that, if absent, would favor cell growth. The Rb protein binds to transcription factors in the nucleus, preventing cells from progressing from the S1 to M stages of the cell cycle. Children born with a 13q14 deletion have only one chromosome encoding Rb; therefore only a single "hit " is required to completely knock out Rb production and lead to the development of retinoblastoma. All of the incorrect choices are proteins encoded by oncogenes, rather than tumor suppressor genes. Oncogenes favor tumorigenesis through overexpression, not deletion. Growth factors (choice B) are oncoproteins that are produced by tumors and have a positive feedback effect. Examples of growth factors are PDGF and fibroblast growth factor; the oncogenes encoding them are sis and hst-1, respectively. The prototypical growth factor-binding protein (choice C) is ras, which is mutated in a large variety of cancers. Ras normally functions as an activator of protein kinases that regulate cell growth. Overactivity of the ras protein is highly mitogenic. Growth factor receptors (choice D) are either expressed as mutant forms or overexpressed in tumors, leading to upregulation of growth. An example of a growth factor receptor oncogene is erb-B2, present in some breast cancers. Transcription activators (choice E) are DNA-binding proteins that promote DNA transcription. Amplification of these oncogenes causes cancer by promoting the transcription of growth-related genes.
27The correct answer is A. The obturator nerve innervates the muscles of the medial compartment of the thigh. These include the adductor longus, adductor brevis, adductor magnus, and gracilis muscles. The adductor magnus is also innervated by the tibial nerve. The biceps femoris (choice B) is in the posterior compartment of the thigh. The long head of the biceps femoris is innervated by the tibial portion of the sciatic nerve, and the short head of the biceps femoris is innervated by the common peroneal portion of the sciatic nerve. The rectus femoris (choice C) and vastus medialis (choice E) are two of the four heads of the quadriceps femoris muscle. All four heads of the quadriceps femoris muscle are in the anterior compartment of the thigh, and are innervated by the femoral nerve. The sartorius muscle (choice D) is in the anterior compartment of the thigh, and is innervated by the femoral nerve.
28The correct answer is A. The patient has Burkitt's lymphoma. This type of lymphoma is a high-grade B-cell lymphoma that occurs in endemic form in Africa (it is the most common neoplasm in children in an equatorial belt that includes Africa and New Guinea) and sporadically in the United States and Europe. The sporadic form is often in an abdominal site and occurs in young adults. The African form of Burkitt's lymphoma has been strongly associated with antibodies directed against Epstein-Barr virus; the association is weaker in sporadic cases. A characteristic translocation, t(8;14) (q24.l3;q32.33) has been described. Hepatitis B (choice B) is associated with hepatocellular carcinoma. t(9;22) is the Philadelphia chromosome, which is seen in some cases of CML and AML. Herpesvirus (choice C) does not have a strong tumor association, although a link to cervical cancer has intermittently been proposed. CD5 is a marker seen in small lymphocytic and mantle cell lymphomas. HIV (choice D) is linked to Kaposi's sarcoma (and AIDS). Some patients also develop primary lymphomas (not usually Burkitt's). CD4 is a marker for helper T cells and some T cell lymphomas. Human papillomavirus (choice E) is linked with common warts, genital condylomata, and genital cancers. t(2;5) is linked to anaplastic large cell lymphoma.
29The correct answer is E. The patient is presenting with hypertension and signs and symptoms of benign prostatic hyperplasia (BPH). The essential diagnostic characteristics of BPH include a decrease in the force and caliber of the urinary stream, nocturia, high post-void residual volume, urinary retention, and azotemia. Terazosin is an alpha-adrenergic antagonist that selectively blocks alpha-1 receptors in vascular smooth muscle producing relaxation. It is indicated for the treatment of both hypertension and BPH. Finasteride (choice A) is a specific inhibitor of 5-alpha reductase, an enzyme that converts testosterone into the potent androgen dihydrotestosterone (DHT) in the prostate gland. This agent is indicated only for the treatment of BPH. Guanfacine (choice B) is a centrally acting alpha-2 agonist indicated for the treatment of mild to moderate hypertension. Hydralazine (choice C) is a vasodilator indicated for the treatment of hypertension and to decrease afterload in patients with congestive heart failure. Labetalol (choice D) is both an alpha- and beta-receptor blocking agent indicated for the treatment of hypertension.
30The correct answer is E. The superior pancreaticoduodenal artery is a branch of the gastroduodenal artery, which is a branch of the common hepatic artery, itself a branch of the celiac trunk. The inferior pancreaticoduodenal artery is a branch of the superior mesenteric artery. Occlusion of the celiac trunk would allow blood from the superior mesenteric artery to reach the branches of the celiac trunk via the connections between the superior and inferior pancreaticoduodenal arteries. The left gastric and right gastric arteries (choice A) both receive their blood from the celiac trunk. The left gastric artery is a direct branch of the celiac trunk. The right gastric artery is usually a branch of the proper hepatic artery, which is a branch of the common hepatic artery (a branch of the celiac trunk). The left and right gastroepiploic arteries (choice B) both receive their blood supply from the celiac trunk. The left gastroepiploic artery is a branch of the splenic artery, which is a branch of the celiac trunk. The right gastroepiploic artery is a branch of the gastroduodenal artery, which is a branch of the common hepatic artery (a branch of the celiac trunk). The proper hepatic and gastroduodenal arteries (choice C) are branches of the common hepatic artery, which is a branch of the celiac trunk. The right colic and middle colic arteries (choice D) are both branches of the superior mesenteric artery.
31The correct answer is C. The only conclusion that can be drawn from this data is that Drug X is less efficacious than Drug Y. Efficacy is defined as the maximum effect that can be produced by a drug, regardless of dose. Drug X can only produce a 50% change in resistance, whereas Drug Y can produce a 75% change in resistance. Therefore, Drug X is less efficacious than Drug Y. A volume of distribution (choice A) is the ratio of the amount of drug in the body to its plasma concentration. In this experiment, we do not know the total amount of drug used or the plasma concentration. For that matter, we do not even know if this is an in vivo experiment. Thus, no conclusions can be drawn about volume of distribution. The half-life (choice B) is the time it takes for the concentration of a drug to fall 50% from its previous measurement. There is no information given to determine half-life. The potency (choice D) is the dose or concentration required to produce 50% of the drug's maximal effect. We cannot determine the potency of Drug Y from this question. The LD50 (choice E) is the dose that causes death in 50% of a population of subject. The experiment described above does not describe a population study, nor does it give any indication about the toxicity of the drug.
32The correct answer is E. Hip fracture and prolonged bed rest are classic risk factors for the development of pulmonary thromboemboli (PE). Common clinical manifestations of PE are hypoxia (due to ventilation/perfusion mismatch) despite a normal chest x-ray, tachycardia, and delirium in older patients. Cerebral hemorrhage (choice A) might cause delirium but would not directly cause hypoxia unless the patient was hypoventilating (e.g., because of brainstem involvement). Cerebral infarction (choice B) could produce delirium but would not directly cause hypoxia unless the patient was hypoventilating. Myocardial infarction (choice C) could account for delirium and tachycardia, but not for hypoxia with a normal chest x-ray. Severe congestive heart failure after myocardial infarction could cause hypoxia due to pulmonary edema, but the chest x-ray would not be normal. Pulmonary infarction (choice D) may cause delirium, tachycardia, and hypoxia, but the chest x-ray may be abnormal. A chest x-ray performed within 12-36 hours after a pulmonary infarct may reveal a peripherally located, wedge-shaped infiltrate.
33The correct answer is A. The woman has a urinary tract infection. Pregnancy can predispose for urinary tract infection by compressing urinary tract structures and partially impairing urinary flow through the urinary tract. The presence of white blood cell casts specifically implies renal involvement, since these form when the leukocytes are compressed together in the renal tubules. Similarly, the presence of red blood cell casts in a bloody urine would indicate that at least some of the bleeding was occurring in the kidney. Infection of other sites in the urinary tract, including ureters (choice B), bladder (choice C), and urethra (choice D), does not cause cast formation. While spread of a urinary tract infection to a pregnant uterus (choice E) is always of concern in a pregnant woman, the presence of casts does not specifically suggest that this has occurred.
34The correct answer is D. This patient is exhibiting the Marcus-Gunn phenomenon. When light strikes the retina, the pupillary light reflex is automatically triggered, leading to simultaneous constriction of both pupils. In the absence of adequate light entering the eye, for example following retinal detachment or optic neuritis, paradoxical dilatation of the pupils occurs. The retina receives far less light than it normally would, and the pupils dilate in order to absorb as much light as possible.
35The correct answer is E. The urachus is the derivative of the allantoic duct, which passes from the urogenital sinus to the umbilical cord. Normally, this duct fuses and is no longer patent. The adult derivative is the median umbilical ligament, which lies in the midline along the interior surface of the anterior abdominal wall. It passes from the upper end of the bladder to the umbilicus. The lateral umbilical fold (choice A) is the fold of parietal peritoneum that covers the inferior epigastric artery and vein on the interior surface of the anterior abdominal wall. The medial umbilical fold (choice B) is the fold of parietal peritoneum that covers the medial umbilical ligament, the adult derivative of the umbilical artery (see below). The medial umbilical ligament (choice C) is the adult derivative of the distal portion of the umbilical artery. The umbilical artery arises from the internal iliac artery. It passes along the bladder and then the anterior abdominal wall to reach the umbilicus. Prenatally, this artery carries fetal blood to the placenta, where it gains oxygen and nutrients. Postnatally, the proximal part of the umbilical artery remains patent and supplies blood to the superior surface of the bladder. Distal to the bladder, the artery becomes fibrotic and is known as the medial umbilical ligament. The median umbilical fold (choice D) is the fold of parietal peritoneum that covers the median umbilical ligament, the adult derivative of the urachus.
36The correct answer is A. Apoptosis refers to programmed cell death, and in this situation, appears to be a means for the elimination of unneeded osteoblasts as the extracellular matrix is reshaped and the healing process continues. Two basic morphologic features of apoptosis are seen in this cell. First, cytoplasmic blebbing, in which round, elongated structures (blebs) extend from the main cell body, is evident. Some blebs appear as though in clusters. Second, nuclear blebbing, in which the nucleus shows the same irregular type of blebs or protrusions, is apparent. This cell does not have features of a macrophage (choice B) such as lysosomes, or a heterogeneous cytoplasm. Ribosome-filled blebs are not features of macrophages. No chromosomes are present, hence this cannot be a dividing cell (choice C). Cytoplasmic and nuclear blebbing are not features of necrosis (choice D). In necrosis, nuclei are washed out (karyolysis), markedly compact (pyknotic), or fragmented (karyorrhexis). A typical osteoblast (choice E) is seen to the left of the blebbing cell. This cell has extensive rough endoplasmic reticulum and a Golgi apparatus with elliptical and round granules.
37The correct answer is A. Features of Down's syndrome (trisomy 21) in children include mental retardation, epicanthal folds, dysplastic ears, hypotonia, a horizontal palmar crease (simian crease), redundant neck skin, and a short trunk. However, most of these children eventually grow to adulthood. At that point, the aging parents may have to deal with a physically strong and healthy mentally retarded individual who is experiencing a deterioration in mental function. This deterioration may be accompanied by aggressive behavior (as in the elderly with Alzheimer's disease) arising out of the patient's diminishing ability to reason or understand his environment. Edwards' syndrome (choice B), or trisomy 18, causes death in infancy. Characteristics include rocker-bottom feet, low-set ears, micrognathia, congenital heart disease, and mental retardation. Fragile X syndrome (choice C) is associated with enlarged testes as well as mental retardation. The condition is unusual in that it is related to expansion of a CGG repeat sequence located on the X chromosome. Patau syndrome (choice D), or trisomy 13, is characterized by severe mental retardation, microcephaly, microphthalmia, polydactyly, cleft lip and palate, renal defects, and cardiac abnormalities. Affected infants typically die before the age of 1. The effects of supernumerary Y chromosomes (choice E; most commonly XYY) include increased stature, aggressive behavior, and infertility, but a supernumerary Y chromosome is sometimes found in otherwise normal individuals.
38The correct answer is A. This woman is afflicted with temporal (giant cell) arteritis. This is a panarteritis that can involve any of the branches of the aortic arch, but which classically affects the branches of the carotid system. Temporal arteritis commonly (40-50%) produces visual disturbances, including blindness due to involvement of the ophthalmic artery. Biopsy of affected segments of arteries may be diagnostic, showing granulomatous lesions with giant cells, although non-specific inflammatory infiltrates and/or intimal fibrosis (generally with no disruption of the internal elastic lamina) are also seen with some frequency. Isolated deafness (choice B) is not commonly seen with temporal arteritis. Stroke may occur in temporal arteritis, but this would not likely produce loss of all tactile sensation (choice C). Loss of the ability to speak (choice D) might conceivably result from a stroke affecting the inferior frontal gyrus, or from a lesion of the brainstem centers controlling phonation, but visual disturbances are more common than stroke in temporal arteritis. Paralysis (choice E) is not a common complication of temporal arteritis.
39The correct answer is E. The ventral pancreatic bud normally rotates around the duodenum to fuse with the dorsal pancreatic bud. Both pancreatic buds form from evaginations from the second part of the duodenum, hence the rotation is around the second part of the duodenum. The normal rotation is around the right side of the embryonic duodenum. Annular pancreas results from the ventral pancreatic bud dividing and rotating around both the right and left sides of the second part of the duodenum, thus encircling it. The dorsal pancreatic bud (choices A, B, and C) does not rotate around the duodenum and therefore is not the cause of annular pancreas. The ventral pancreatic bud does not form from the first part of the duodenum (choice D) and therefore does not rotate around this part of the duodenum.
40The correct answer is B. The patient's clinical presentation is typical of primary atypical pneumonia. In contrast to bacterial pneumonia, primary atypical pneumonia presents with the following features: - Caused by M. pneumoniae; less frequently by viruses (influenza, respiratory syncytial virus, adenovirus, rhinoviruses, rubeola and varicella virus), Chlamydia, or Coxiella burnetii - Characterized pathologically by interstitial, rather than intra-alveolar, inflammation - Characterized clinically by nonspecific symptomatology and few "localizing" symptoms Why is M. pneumoniae, and not influenza virus (choice A) or respiratory syncytial virus (choice D), the cause of this patient's pneumonia? First, M. pneumoniae infections are often associated with the appearance of cold agglutinins in the serum, detection of which is diagnostically important. Second, the patient responded quickly to treatment with erythromycin, an antibiotic effective against M. pneumoniae, but obviously not effective in treating viral infections. Pneumocystis carinii (choice C) is a fungal organism causing pneumonia in severely immunocompromised hosts, especially AIDS patients. P. carinii pneumonia (PCP) is characterized by accumulation of a frothy exudate containing numerous organisms within alveolar spaces. Also, P. carinii is not sensitive to erythromycin. The drug of choice for treatment of PCP is trimethoprim-sulfamethoxazole. Streptococcus pneumoniae (choice E) is the usual causative agent of lobar pneumonia, characterized by consolidation of a single lobe due to intra-alveolar acute inflammatory exudation. Lobar pneumonia is more prevalent in young, healthy individuals, whereas primary atypical pneumonia favors old, debilitated patients. S. pneumoniae is highly sensitive to penicillin.
41The correct answer is A. Cholecystokinin, or CCK, is synthesized in the duodenal and jejunal mucosa and stimulates gall bladder contraction and pancreatic enzyme secretion. Other functions include slowing of gastric emptying, an atrophic effect on the pancreas, and secretion of antral somatostatin, which in turn, decreases gastric acid secretion. Gastric inhibitory peptide, or GIP (choice B), stimulates pancreatic insulin secretion at physiologic doses and inhibits gastric acid secretion and gastric motility at pharmacologic doses. Gastrin (choice C) prepares the stomach and small intestine for food processing, including stimulating secretion of HCl, histamine, and pepsinogen. It also increases gastric blood flow, lower esophageal sphincter tone, and gastric contractions. Secretin (choice D) stimulates secretion of bicarbonate-containing fluid from the pancreas and biliary ducts. Vasoactive intestinal polypeptide, or VIP (choice E), relaxes intestinal smooth muscle and stimulates gut secretion of water and electrolytes.
42The correct answer is D. This patient expresses feelings of anxiety which are only relieved by compulsive ritual behavior (checking the doors and windows excessively). Adjustment disorder with anxiety (choice A) generally occurs in response to an identifiable stressor. Agoraphobia without a history of panic disorder (choice B) is characterized by a fear of all large enclosed or open spaces when alone. In generalized anxiety disorder (choice C), excessive worry or anxiety is present most of the time the person is awake, not just in a specific situation. In panic disorder with agoraphobia (choice E), panic attacks occur in uncued situations. This patient's symptoms appear consistently when she leaves for work in the morning.
43The correct answer is E. Bone marrow suppression, diarrhea, and alopecia are the most common side effects seen with cancer chemotherapy regimens. Vincristine, a mitotic inhibitor, is a chemotherapeutic agent that is not associated with the development of bone marrow suppression and would be the most appropriate agent to use in this patient. Vincristine is effective in the treatment of acute lymphoblastic leukemia and other leukemias, Hodgkin's disease, lymphosarcoma, neuroblastoma, and various other types of cancer. Bleomycin is another antineoplastic agent that does not cause bone marrow suppression. Busulfan (choice A) is an alkylating agent primarily used in the palliative treatment of chronic myelogenous leukemia; it is known to cause severe bone marrow suppression. As a general rule, the alkylating agents typically produce severe immunosuppressive effects. Cisplatin (choice B) is another alkylating agent indicated for the treatment of metastatic testicular and ovarian tumors in combination with other agents. This agent can also cause profound bone marrow suppression. Cyclophosphamide (choice C) is classified as a nitrogen mustard, a subcategory of the alkylating agents. It is primarily used to treat breast, testicular, and other solid tumors, as well as leukemia and lymphoma. This drug suppresses bone marrow. Paclitaxel (choice D) is an antimicrotubule agent typically used in the treatment of ovarian and breast cancer. Profound neutropenia is typically seen with this agent.
44The correct answer is B. Lactic acidosis, characterized by elevated blood lactate, decreased arterial blood pH, decreased bicarbonate, and electrolyte imbalances with an elevated anion gap (normal = 10 - 12), is a rare but serious complication of metformin administration. The onset of lactic acidosis is usually accompanied by several non-specific signs and symptoms including malaise, myalgias, respiratory distress and increased somnolence. There may be associated hypothermia, hypotension, and resistant bradyarrhythmias as the condition progresses. Glyburide (choice A) is a sulfonylurea associated with the development of hypoglycemia and cholestatic jaundice (a rare complication). Miglitol (choice C) is an alpha-glucosidase inhibitor commonly associated with the development of abdominal discomfort and flatulence. Repaglinide (choice D) is the non-sulfonylurea moiety of glyburide; it is commonly associated with hypoglycemia, nausea and vomiting. Idiosyncratic hepatocellular injury has been reported during the usage of troglitazone (choice E). The hepatic injury is usually reversible, but rare cases of hepatic failure requiring liver transplantation or leading to death have been reported with this agent.
45The correct answer is A. The dermis contains skin appendages (e.g., hair follicles) that contain epithelial stem cells. In the process of healing a large area where the epidermis has been lost, but the dermis is intact, re-epithelialization occurs by ingrowth of epidermal cells from the underlying skin appendages, as well as from the intact epidermis along the wound edges. None of the other cell types are known to directly contribute to the regeneration of epidermis over abraded skin.
46The correct answer is D. A forced expiration is the simplest test of lung function. The individual breathes in as much air as the lungs can hold and then expels the air as rapidly and as far as possible. The forced vital capacity (FVC) is the vital capacity measured with a forced expiration (FVC = 3 L for patient Y). The forced expiratory volume in one second (FEV1) is the amount of air that can be expelled from the lungs during the first second of a forced expiration (FEV1 = 2.7 L for patient Y). The FEV1/FVC ratio has diagnostic value for differentiating between normal, obstructive, and restrictive patterns of a forced expiration. The FEV1/FVC ratio for the healthy individual (X) is 4 L/5 L = 80% and the FEV1/FVC for patient Y is 2.7/3.0 = 90%. FEV1/FVC is a function of airway resistance. Increases in airway resistance associated with asthma (choice A), bronchospasm (choice B), emphysema (choice C), and old age (choice E) tend to decrease the FEV1/FVC ratio below its typical normal value of 80%. FEV1/FVC is often increased with interstitial fibrosis because of increased radial traction of the airways, i.e., the airways are held open to a greater extent at any given lung volume, reducing their resistance to air flow. The increase in elastic recoil also makes it difficult to breathe deeply, which decreases FVC. This combination of decreased FVC along with normal or slightly increased FEV1/FVC is characteristic of fibrotic lung disease.
47The correct answer is D. The malignant skin tumor that forms "pearly papules" on sun-exposed skin is basal cell carcinoma. A characteristic feature of this tumor is palisading of the basal cell-like nuclei at the edge of clusters of cells penetrating into the dermis. Basal cell carcinomas almost never metastasize, but can be very locally destructive, and resection of large ones on the face may produce disfiguring scars. Viral cytoplasmic inclusions (choice A) are a feature of the infectious lesion molluscum contagiosum. Keratin pearls (choice B) are a feature of squamous cell carcinoma. Melanin (choice C) and S-100 positivity (choice E) with immunohistochemical stains are features of melanoma.
48The correct answer is A. The diseases listed in the answers are all inherited disorders of bilirubin metabolism that are usually discussed together. Crigler-Najjar syndrome (choices A and B) and Gilbert's syndrome (choice D) are both unconjugated hyperbilirubinemias, while Dubin-Johnson syndrome (choice C) and Rotor syndrome (choice E) are conjugated hyperbilirubinemias. Crigler-Najjar syndrome (particularly the type I variant) is rare and extremely serious (with the presentation given in the question stem) while Gilbert's syndrome is completely benign. The type II variant of Crigler-Najjar is intermediate in severity between Gilbert's and the Type I. Dubin-Johnson and Rotor syndrome are also relatively benign; Dubin-Johnson is distinguished from Rotor syndrome by the presence of a black pigment of unknown composition in the liver.
49The correct answer is A. The patient is presenting with signs and symptoms of fibrositis (fibromyalgia). This disorder is most commonly seen in women between the ages of 20 and 50, and is associated with widespread chronic musculoskeletal pain that improves with exercise, chronic fatigue, and sometimes, severe headaches. Examination typically reveals painful trigger points produced by palpation of the trapezius and the lateral epicondyle of the elbow. Objective signs of inflammation are absent and laboratory studies are normal. Patients with this disorder are likely to respond to treatment with tricyclic antidepressants or skeletal muscle relaxants with strong anticholinergic side effects, such as cyclobenzaprine. One of the most effective agents in the treatment of this disorder is amitriptyline, a tricyclic antidepressant commonly used in the treatment of depression, and as an adjunctive pain medication. Cefaclor (choice B) is a second generation cephalosporin. Since fibromyalgia is not an infectious disorder, this agent would be ineffective in this patient. Naproxen (choice C) is a non-steroidal anti-inflammatory drug indicated for the treatment of mild-to-moderate pain. NSAIDs are generally ineffective in the treatment of this disorder. Oxycodone (choice D) is an opioid analgesic indicated for the treatment of moderate to severe pain; opioids are ineffective in the treatment of fibromyalgia. Prednisone (choice E) is a corticosteroid indicated for the treatment of a variety of disorders caused by inflammation. Since this disease is not an inflammatory condition, prednisone would be not be indicated for this patient.
50The correct answer is B. Pyridoxine, or vitamin B6, is sometimes depleted with isoniazid (INH) use. Patients with pyridoxine deficiency may experience neurologic symptoms, such as convulsions and fasciculations. The treatment of this disorder is slow IV administration of 2-5 g of pyridoxine. Niacin (choice A) deficiency, also known as pellagra, is a disease that involves several organs, including the skin, the gastrointestinal system, and the nervous system. A useful mnemonic for remembering the symptoms of pellagra is the "4 D's": dermatitis, dementia, diarrhea, and death. These symptoms are not consistent with the patient history described in the question. Riboflavin (choice C) deficiency is not typically seen alone, but rather in conjunction with other vitamin deficiencies. Dermatitis and glossitis are the most frequent clinical manifestations. Thiamine (choice D) deficiency, or beri-beri, presents with dry skin and paralysis, rather than convulsions. Severe thiamine deficiency produces Wernicke's encephalopathy, with disorientation, ataxia, and ophthalmoplegia. This deficiency is typically seen in alcoholic patients. Vitamin C (choice E) deficiency, or scurvy, causes defective growth and maintenance of gums, blood vessels, joints, and teeth. These symptoms are due to impaired collagen hydroxylation, a process that requires vitamin C.