USMLE USMLE Certifications USMLE Questions & Answers

• Question 211:

  A 75-year-old man presents to his physician with complaints of nocturia, urinary urgency, and a feeling that he could not completely empty his bladder. A digital rectal exam reveals a firm, enlarged prostate. A bone scan is ordered and shows positivity in multiple vertebral bodies. Elevation of which of the following substances would be most strongly associated with the development of bone lesions?

  A. Prostatic acid phosphatase

  B. Prostate-specific antigen

  C. Serum alkaline phosphatase

  D. Tartrate-resistant acid phosphatase

  E. Urinary hydroxyproline

  Correct Answer: C

  Explanation: The patient has prostate cancer causing osteoblastic bone lesions. Osteoblastic cells respond to metastatic prostate carcinoma by forming bone (osteoid) and secreting alkaline phosphatase, which is thought to either initiate or facilitate mineralization. Prostatic acid phosphatase and prostatic-specific antigen are not correct because they do not answer the question being asked. The question asks for bone metabolites related to the patients skeletal metastasis. These two markers are synthesized by the tumor and would most likely be elevated in this case; however, they are elevated because of the prostatic cancer, independent from the bony metastasis. Tartrate-resistant acid phosphatase and urinary hydroxyproline are metabolic markers of osteoclastic (not osteoblastic) cell activity. Lytic tumor metastasis (lung, kidney, gastrointestinal tract, melanoma) would be associated with increased levels of these markers. Tartrateresistant acid phosphatase is secreted by the osteoclast during bone resorption. Hydroxyproline is associated with collagen breakdown, and increased levels are excreted in the urine.

• Question 212:

  A 2-year-old child with uncomplicated coarctation of the aorta appears to be in good health. Growth and development are normal. The constriction is located just distal to the subclavian arteries. Which of the following is decreased in this patient?

  A. Blood flow in the lower body

  B. Blood flow in the upper body

  C. Blood pressure in the upper body

  D. Vascular resistance in the lower body

  E. Vascular resistance in the upper body

  Correct Answer: D

  Explanation:

  In fully compensated aortic coarctation, blood flow is normal in the lower and upper body despite an increased arterial pressure (about 50% higher) in the upper body compared with the pressure in the lower body. Because resistance = pressure/blood flow, it is clear that resistance must be lower in the lower portions of the body. The mechanism of this decrease in resistance below the constriction (and increased resistance above the constriction) is autoregulation of blood flow. The small arteries and arterioles dilate (or constrict) in accordance with the metabolic needs of the tissues, ensuring that each tissue receive an adequate amount of blood flow. Thus, the increase in blood pressure in the upper body leads to constriction of the arterioles, which increases vascular resistance, and the lower pressure below the coarctation leads to dilation of the arterioles, which decreases vascular resistance.

• Question 213:

  A neonate does not pass meconium until 48 hours after his birth. Two weeks later his mother reports that he has not been passing stool regularly. Anorectal manometry reveals increased internal anal sphincter pressure on rectal distention with a balloon. Radiographic studies reveal massive dilation of the colon proximal to the rectum. The findings in this case indicate a developmental abnormality of which of the following embryonic tissues?

  A. Ectoderm

  B. Endoderm

  C. Neural crest

  D. Neural ectoderm

  E. Splanchnic mesoderm

  Correct Answer: C

  Explanation:

  The infant has Hirschsprung disease, which is due to an absence of ganglion cells in the wall of the colon. Neural crest cells contribute to the formation of many adult structures. Among these are all of the postganglionic neurons of the autonomic nervous system and the sensory neurons of the peripheral nervous system. Ectoderm forms the epidermis of the skin and the parenchymal cells of glands associated with the skin, such as the sweat glands, sebaceous glands, and mammary glands. Endoderm forms the epithelial lining of the gut tube and the parenchymal cells of glands associated with the gut tube, such as the liver and pancreas. Neural ectoderm forms the CNS, the somatic motor neurons of the peripheral nervous system, and the preganglionic neurons of the autonomic nervous system. Splanchnic mesoderm forms the visceral peritoneum, the visceral pleura, the visceral pericardium, and the stroma and muscle of the wall of the gut, among other structures.

• Question 214:

  A 75-year-old woman presents to the physician with a chief complaint of vaginal spotting. She has been postmenopausal for 25 years and does not take hormones. An ultrasound shows a mass in the uterine fundus. A hysterectomy is performed, and pathologic examination of the removed uterus reveals a malignant tumor of the endometrial glands and stroma. Which of the following is the most likely diagnosis?

  A. Endolymphatic stromal myosis

  B. Endometrial carcinoma

  C. Endometrial stromal sarcoma

  D. Leiomyosarcoma

  E. Malignant mixed mullerian tumor

  Correct Answer: E

  Explanation:

  Malignant mixed mullerian tumor is a tumor with two components, stromal and epithelial (endometrial glands), both of which are malignant. This is a rare and highly aggressive tumor that has a 25% 5-year survival rate. It usually affects older patients and presents with postmenopausal bleeding. The stromal component can contain metaplastic components such as cartilage and bone. Interestingly, usually only the epithelial component metastasizes. Endolymphatic stromal myosis is a type of endometrial stromal tumor of intermediate malignancy. It appears as small pieces of stroma between myometrial bundles that infiltrate lymph channels. Patients may have pain or bleeding, or may be asymptomatic. Recurrences happen late in the course of the disease (years) in 50% of patients, and metastasis occurs in 15%. There is no epithelial component, so this is an incorrect choice. Endometrial carcinoma is a malignancy of the epithelial glandular component of the endometrium. Abnormal bleeding is the usual presentation. High estrogen states cause this tissue to proliferate. There is no stromal component of this tumor, so this is an incorrect choice. Endometrial stromal sarcoma is a true sarcoma arising from the endometrial stroma that infiltrates the myometrium and invades vessels. There is no epithelial component. Leiomyosarcoma is a true sarcoma arising from the uterine smooth muscle. It commonly has satellite lesions within the uterus. Leiomyosarcomas usually recur after removal; survival is greater with well-differentiated lesions. Poorly differentiated lesions have a 10% to 15% 5-year survival rate. Distant metastasis is via blood vessels. There is no epithelial component.

• Question 215:

  A 65-year-old man develops oliguria and peripheral edema over a period of weeks. Urinalysis reveals hematuria and proteinuria; examination of the urinary sediment reveals red cell casts. Radiologic and ultrasound studies fail to demonstrate an obstructive lesion. Renal biopsy shows many glomerular crescents. This presentation is most suggestive of which of the following conditions?

  A. Anti-glomerular basement membrane disease

  B. Minimal change disease

  C. Diabetic nephropathy

  D. Hypertensive nephropathy

  E. Lupus nephritis

  Correct Answer: A

  Explanation:

  The two principal causes of rapidly progressive glomerulonephritis are anti-glomerular basement membrane (including both Good pasture syndrome and isolated anti-glomerular basement disease) and primary systemic vasculitis (including Wegener granulomatosis, microscopic polyarteritis, idiopathic rapidly progressive glomerulonephritis, Churg-Strauss syndrome, polyarteritis nodosa, giant-cell arteritis, and Takayasu arteritis). A very large variety of other systemic and primary glomerular disease may occasionally cause rapidly progressive glomerulonephritis, but this is usually not the typical presentation for these diseases. Diabetic nephropathy typically begins with microalbuminuria and hypertension and progresses over a 10- to 20-year period to renal failure. Hypertensive nephropathy due to essential hypertension typically presents with slowly rising BUN and creatinine; hypertensive nephropathy due to malignant hypertension presents with more rapidly rising BUN and creatinine. Lupus nephritis can have many presentations, but the most typical is proteinuria, which may be severe enough to cause nephrotic syndrome. Also, 90% of cases of systemic lupus erythematosus occur in women, usually of child-bearing age. Minimal change disease typically presents with nephrotic syndrome and is not consistently associated with recognizable glomerular changes by light microscopy. Podocyte foot-process fusion can be seen by electron microscopy.

• Question 216:

  A couple has a daughter who is ataxic and has a seizure disorder. She also has a strange affect characterized by excessive laughter at inappropriate times. Cytogenetic analysis demonstrates a normal genotype with 46 chromosomes and no apparent deletions. These symptoms are most likely due to:

  A. confined placental mosaicism

  B. expansion of a trinucleotide repeat

  C. a point mutation in an autosome

  D. random inactivation of the X chromosome

  E. uniparental disomy

  Correct Answer: E

  Explanation:

  The child described is exhibiting the features of Angelman (happy puppet) syndrome. This disorder is generally caused by a deletion of band q12 in the maternal copy of chromosome 15, i.e., [(del (15) (q11q13)]. A similar deletion in the paternal chromosome 15 produces Prader-Willi syndrome. The disparate expression of the effects of deletions in the paternal vs. the maternal chromosomes, called genomic imprinting, implies that the same genetic loci are expressed quite differently in maternal and paternal chromosomes. Angelman syndrome can also occur if uniparental disomy occurs for chromosome 15, such that the embryo receives two copies of the maternal chromosome 15 without the paternal chromosome 15 to “balance” the maternal contribution. Confined placental mosaicism is due to a mutation occurring within trophoblast or extraembryonic precursor cells of the inner cell mass and is an important cause of intrauterine growth retardation. Expansion of a trinucleotide repeat is associated with Fragile X syndrome and Huntington disease. Point mutation in autosomes has not been associated with Angelman syndrome. Random inactivation of the X chromosome occurs normally, as postulated in the Lyon hypothesis.

• Question 217:

  A 25-year-old man presents to a rheumatologist with complaints of joint pain involving the large joints of the legs. On questioning, the patient indicates that exacerbations in the joint pain are frequently accompanied by diarrhea. Which of the following is the most likely diagnosis?

  A. Amebic colitis

  B. Chronic appendicitis

  C. Diverticulosis

  D. Pseudomembranous colitis

  E. Ulcerative colitis

  Correct Answer: E

  Explanation: Several gastrointestinal diseases are associated with rheumatologic complaints. The most frequent of these are the chronic inflammatory bowel diseases, ulcerative colitis, and Crohn disease, which can be associated with sacroiliitis (related to HLA-B27) or lower limb arthritis. Other gastrointestinal diseases associated with arthropathy include bypass surgery, Whipple disease, Behcet syndrome, and celiac disease. Amebic colitis is caused by ingestion of infectious cysts (typically from Entamoeba histolytica). Symptoms include abdominal pain and diarrhea; malaise and weight loss also may occur. Cecal amebiasis can resemble acute appendicitis. Chronic appendicitis may be asymptomatic or cause poorly defined abdominal pain. Diverticulosis is usually a disease of older adults. It is often asymptomatic unless inflammation supervenes. Pseudomembranous colitis is a severe form of diarrhea usually seen in the setting of prior antibiotic use. The causative organism is almost always Clostridium difficile.

• Question 218:

  A letter carrier is severely bitten by a pit bull guarding a junkyard. The wound is cleansed, and the letter carrier receives a booster injection of tetanus toxoid and an injection of penicillin G. Several days later, the wound is inflamed and purulent. The exudate is cultured on blood agar and yields gram-negative rods. Antibiotic sensitivity tests are pending. The most likely agent to be isolated is

  A. Bartonella henselae

  B. Brucella canis

  C. Clostridium tetani

  D. Pasteurella multocida

  E. Toxocara canis

  Correct Answer: D

  Explanation:

  Pasteurella multocida is a gram-negative rod that is normal flora of the oral cavity of dogs and cats. It often causes a local abscess following introduction under the skin by an animal bite. Most cases occur in children who are injured while playing with a pet. Bartonella henselae is a very small, gram-negative bacterium that is closely related to the rickettsia, although it is able to grow on lifeless media. It is the cause of cat-scratch disease (a local, chronic lymphadenitis most commonly seen in children) and bacillary angiomatosis (seen particularly in AIDS patients). In this latter patient population, the organism causes proliferation of blood and lymphatic vessels causing a characteristic “mulberry” lesion in the skin and subcutaneous tissues of the afflicted individual. Brucella canis is a gram-negative rod that is a zoonotic agent. Its normal host is the dog. When it gains access to humans, however, it causes an undulating febrile disease with malaise, lymphadenopathy and hepatosplenomegaly. The normal route of exposure is via ingestion of the organism. Clostridium tetani is a gram-positive spore-forming anaerobic rod. It causes tetanus [a spastic paralysis caused by tetanospasmin, which blocks the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA)]. There may be no lesion at the site of inoculation, and exudation would be extremely rare. Toxocara canis, a common intestinal parasite of dogs, is a metazoan parasite that causes visceral larva migrans. Young children are most likely to be affected, as they are most likely to ingest soil contaminated with eggs of the parasite.

• Question 219:

  The parents of a 7-year-old boy divorce. The boy lives with the mother and sees his father every-other weekend. During these visits, the boy is sullen and angry with the father, but when it is time to return home, he clings to the father and cries in a desperate manner while saying “I’m sorry! I want you and mom to live together again.” Which of the following is the most helpful statement that the father can make to the son?

  A. “Big boys don't cry.”

  B. “I left your mother, I didn't leave you.”

  C. “I’ll see you in 2 weeks.”

  D. “You’re the man of the house now.”

  E. “Your mother was too hard to live with.”

  Correct Answer: B

  Explanation:

  This statement from the father would reflect his understanding of the egocentric nature of school-aged children. That is, the child is assuming that he is responsible for the divorce between his parents. The anger and withdrawal reflect the child's frustration with the situation, but the tears and apology suggest the child's fear and assumed responsibility for the breakup. “Big boys don't cry” is a demeaning and belittling statement. “I’ll see you in 2 weeks” ignores the child's felt responsibility for the divorce. “You’re the man of the house now” places too much responsibility on a 7-year-old child. “Your mother was too hard to live with” places all the blame and responsibility for the divorce on the parent, with whom the boy lives on a daily basis. It ignores the reality that divorce is usually due to difficulties that both parents have with each other.

• Question 220:

  A 2-month-old child is evaluated for failure to thrive. During the examination, the child has a seizure. Stat serum chemistries demonstrate severe hypoglycemia, hyperlipidemia, lactic acidosis, and ketosis. Physical examination is remarkable for hepatomegaly, a finding confirmed by CT scan, which also reveals renomegaly. Which of the following diseases best accounts for this presentation?

  A. Gaucher disease

  B. McArdle disease

  C. Niemann-Pick disease

  D. Pompe disease

  E. Von Gierke disease

  Correct Answer: E

  Explanation:

  Von Gierke disease is a glycogen storage disease caused by a deficiency of glucose-6-phosphatase. It typically presents with neonatal hypoglycemia, hyperlipidemia, lactic acidosis, and ketosis. Failure to thrive is common in early life; convulsions may occur because of profound hypoglycemia. The glycogen accumulation in von Gierke disease occurs primarily in the liver and kidneys, accounting for the enlargement of these organs. Gout may develop later because of the derangement of glucose metabolism. Even if you do not remember all the details of the presentation of these genetic diseases, you should be able to narrow the choices: Gaucher disease and Niemann-Pick disease are lipid storage diseases and would not be expected to produce hypoglycemia. The other diseases are glycogen storage diseases, but both McArdle and Pompe diseases affect muscle rather than liver and would not be expected to produce profound hypoglycemia, since the liver is the major source for blood glucose.