USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 311:

  A 72-year-oldman with a known history of chronic essential hypertension dies unattended at home. The medical examiner determines the cause of death to be hypertensive intracerebral hemorrhage. The most likely site of the hemorrhage is which of the following?

  A. basal ganglia or thalamus

  B. cerebellum

  C. frontal lobe

  D. occipital lobe

  E. pons

  Correct Answer: A

  Section: Pathology and Path physiology About 65% of hypertensive intracerebral hemorrhages occur within the basal ganglia or thalamus. Chronic hypertension predisposes to weakening of arteriole walls with subsequent production of CharcotBouchard aneurysms. A rupture of these aneurysms frequently results in fatal intracerebral hemorrhage. The cerebellum (choice B) is the site of hypertensive hemorrhage about 8% of the time. Hypertensive hemorrhages are very rare in the frontal lobe (choice C) and in the occipital lobe (choice D). The pons (choice E) is the site of hypertensive hemorrhage about 15% of the time.

• Question 312:

  The bone marrow biopsy depicted in below figure was obtained from an infant with hepatosplenomegaly and mental retardation. The pathologic basis of this disorder is best explained by which of the following?

  

  A. deficient cellular immunity that permits continued intracellular bacterial proliferation

  B. exposure to excessive radiation during embryogenesis

  C. hereditary defect of a catabolic enzyme leading to abnormal intracellular accumulation of lipids

  D. oncogenic viral integration into host's DNA that initiates unregulated cellular proliferation

  E. traumatic injury during delivery

  Correct Answer: C

  Section: Pathology and Path physiology figure depicts macrophages filled with lipids from an infant with Gaucher disease. The disease is due to a genetic lack of the catabolic enzyme glucocerebrosidase, which fosters the abnormal accumulation of glucocerebroside within the reticuloendothelial cells and neurons. Gaucher disease is not caused by deficient cellular immunity (choice A), radiation (choice B), viral infection (choice D), or trauma (choice E).

• Question 313:

  A 63-year-old woman has a routine chest x-ray that reveals a suspicious subpleural lesion. The lesion is resected and sectioned, and reveals all (choices A through F) of the following microscopic findings. Which of these findings would most strongly indicate that the lesion is a malignant neoplasm?

  A. hyperchromatism

  B. increased nuclear/cytoplasmic ratio

  C. invasion

  D. mitoses

  E. necrosis

  F. pleomorphism

  Correct Answer: C

  Section: Pathology and Path physiology One might see all of these microscopic findings in a malignant neoplasm, but invasion is the strongest indicator. Hyperchromatism (choice A) is a typical finding in malignant cells indicating their increased DNA content. However, it is not a reliable marker for malignancy. Increased nuclear/cytoplasmic ratio (choice B) can also be seen as part of the normal proliferative response. Mitoses (choice D) indicate an increased proliferative rate, but again the proliferation is not necessarily neoplastic. Necrosis (choice E) is often a feature of rapidly dividing tumors but is also found with infarction, infection, and other conditions. Pleomorphism (choice F) is another feature that is common in malignant tumors, but it can be seen in nonneoplastic conditions and there are some malignancies that are fairly monomorphic.

• Question 314:

  A 26-year-old man presents with a 3-week history of increasing pain just below his right knee. He does not recall sustaining any trauma to his leg and is not experiencing pain elsewhere; he states that he is otherwise healthy. Examination reveals only tenderness to palpation in the area. An x-ray of his right knee demonstrates a small lytic lesion in the tibial medial condyle surrounded by a focus of sclerosis. Based on this information, what is the most likely diagnosis?

  A. gout

  B. osteochondroma

  C. osteomyelitis

  D. osteosarcoma

  E. rheumatoid arthritis

  Correct Answer: C

  Section: Pathology and Path physiology Bacteria are the principle cause of osteomyelitis, infecting bone either by direct penetration (e.g., puncture), extension from a surrounding area (e.g., cellulitis), or via hematogenous spread of an overt infection (e.g., sinusitis, pneumonia) or an occult bacteremia (e.g., mouth, intestinal flora); the leading causative pathogen is S. aureus. Long bone metaphyses are commonly infected in children, whereas long bone epiphyses and vertebrae are more typically affected in adults. Presentation may be limited to pain, with or without fever. The classic x-ray findings include lytic changes caused by necrotic bone (sequestrum) and sclerosis due to the ingrowth of fibrous tissue as new bone growth (involucrum) forms around the devitalized bone. Gout (choice A) is associated with hyperuricemia, leading to acute synovial inflammation and deposition of urate crystals in joint spaces; similarly, rheumatoid arthritis (choice E) is an autoimmune disorder affecting the synovial lining of various joints (chronic synovitis). Osteosarcomas (choice D) are typically large, bulky malignancies most commonly originating in long bone metaphyses, often with secondary spread into epiphyseal regions. Osteochondromas (choice B) are benign tumors arising near the growth plate in endochrondrally derived long bones which form bony, pedunculated, cartilage-capped lesions.

• Question 315:

  A 32-year-old man is admitted for neuropsychiatric evaluation after exhibiting bizarre behavior. During his medical workup, he is found to have cirrhosis and a mild parkinsonian tremor. Which of the following diagnoses provides the best explanation for these findings?

  A. congenial hepatic fibrosis

  B. peliosis hepatis

  C. primary sclerosing cholangitis

  D. Reye syndrome

  E. Wilson disease

  Correct Answer: E

  Section: Pathology and Path physiology Wilson disease is an autosomal recessive disorder of copper metabolism due to defective biliary excretion of the copper-protein complex ceruloplasmin. Cells of the liver and brain, notably the basal ganglia, are particularly vulnerable to the toxic effects of excessive copper accumulation. Treatment with copper chelating agents, such as penicillamine or triethylene tetramine, has a dramatically beneficial effect. Congenital hepatic fibrosis (choice A) is a rare disorder of unknown etiology. It is most prevalent in India. Peliosis hepatis (choice B) is a rare hepatic circulatory disorder caused by dilation of sinusoids, resulting in small, blood-filled spaces within the liver; the condition is typically asymptomatic. Steroid hormone usage is associated with its development in some instances. Primary sclerosing cholangitis (choice C) is due to chronic inflammation and fibrosis of intra- and extrahepatic bile ductules. The etiology is obscure. Most of those affected also have ulcerative colitis. Reye syndrome (choice D) refers to acute hepatic failure in children following ingestion of aspirin for certain upper respiratory illnesses, particular influenza, or chickenpox.

• Question 316:

  A 45-year-oldman is admitted to the hospital for elective gastrointestinal surgery. On the third postoperative day, the patient experiences a fever of 101.5癋, and reports having a slight cough, but is otherwise asymptomatic. Chest x-ray demonstrates a small, interstitial infiltrate in the left lower lobe. Three sets of blood cultures (two bottles each) are drawn and sent to the laboratory. Culture results report positive Staphylococcus epidermidis growth from one bottle of the first culture set, and negative growth from the second and third culture sets. Based on this information, which of the following is the best interpretation of these blood culture results?

  A. intermittent bacteremia associated with postsurgical abscess formation

  B. postoperative septicemia secondary to infective endocarditis

  C. postoperative septicemia secondary to pneumonia

  D. postoperative septicemia secondary to surgical manipulation of the gastrointestinal tract

  E. skin flora contamination and not septicemia

  Correct Answer: E

  Section: Pathology and Path physiology True positive blood cultures are defined by positivity in multiple cultures in a series, whereas contaminates generally are not found in repeat cultures. For example, finding S. epidermidis (found in normal skin flora) in only one bottle of six in three blood culture sets (as in this patient) most probably represents skin contamination. If, however, S. epidermidis were isolated from all six bottles drawn from a patient suspected of having infectious endocarditis, this would be interpreted as a true positive. Thus, the results do not support a diagnosis of either bacteremia or septicemia (choices A through D).

• Question 317:

  A 21-year-old woman presents with a 6-hour history of left-sided lower abdominal pain and is found to be hypotensive. A hemorrhagicmass is discovered in her left fallopian tube during laparoscopy. The tube is surgically excised. A photomicrograph of the tubal contents is displayed in below figure. Which of the following is the most likely diagnosis?

  

  A. chorioadenoma destruens

  B. choriocarcinoma

  C. ectopic tubal pregnancy

  D. granular cell tumor

  E. leiomyoma

  Correct Answer: C

  Section: Pathology and Path physiology figure displays viable benign chorionic villi that are diagnostic of an ectopic tubal pregnancy. The clinical history of acute lower abdominal pain and hypotension are expected findings with an ectopic pregnancy. Chorioadenoma destruens (choice A) is also referred to as invasive mole, and would display invasion of chorionic elements into the uterine, not tubal, muscular layers. Choriocarcinoma (choice B) is a malignant neoplasm composed of gestational trophoblastic tissue. Figure displays benign chorionic elements. Granular cell tumor (choice D) is a neoplasm of neuraltype tissue. The photomicrograph is incompatible with this diagnostic consideration. Leiomyomas (choice E) rarely occur in the fallopian tube. They are most commonly seen in the wall of the uterus. Bundles of benign smooth muscle cells are seen microscopically.

• Question 318:

  A 9-year-old boy is stung on the arm by a wasp and very rapidly develops redness and swelling at the site of the sting. Which of the following substances is most responsible for these early changes?

  A. bradykinin

  B. complement 3a

  C. histamine

  D. leukotriene

  E. thromboxane

  Correct Answer: C

  Section: Pathology and Path physiology Histamine is a preformed inflammatory mediator found principally in mast cells and basophils that has a major role in the early vascular changes of inflammation; that is, dilation of precapillary arterioles which produces the local redness (rubor) and warmth (calor), and the increased permeability of postcapillary venules which produces the swelling (tumor). Bradykinin (choice A) has similar effects to histamine, but it is produced by the activation of the kinin system so it is not immediately available as is histamine. Complement 3a (choice B) and complement 5a are called anaphylatoxins because they can stimulate the release of histamine from mast cells. Leukotriene B4 (choice D) is a major activator and chemotactic agent for leukocytes and potentiates their adhesion to vessel walls. Thromboxane A2 (choice E) promotes platelet aggregation and vasoconstriction; it functions in opposition to prostaglandin, which inhibits platelet aggregation and causes vasodilation.

• Question 319:

  A 3-year-old girl develops gastroenteritis and a number of other children at the day care nursery that she attends are also affected. This was most likely caused by which of the following agents?

  A. Balantidium coli

  B. Cryptosporidium parvum

  C. Entamoeba histolytica

  D. Giardia lamblia

  E. rotavirus

  Correct Answer: E

  Section: Pathology and Path physiology Rotavirus is the most common cause of severe diarrhea worldwide and is most widespread in very young children. It is passed readily to others and can result in outbreaks such as described here. B. coli (choice A) is a ciliated intestinal protozoal parasite that is found mostly in the tropics. It is a rare cause of diarrhea in the United States. C. parvum (choice B) is a spore-forming protozoan that can cause severe diarrhea in immunocompromised individuals. E. histolytica (choice C) is another protozoan parasite. It infests the colon forming flask-shaped ulcers (i.e., having narrow neck and a wide base that undermines the adjacent mucosa). These organisms can also be carried in the portal circulation to the liver where they form characteristic "anchovy paste" abscesses. G. lamblia (choice D) is an intestinal flagellate that infests the upper small intestine. It is very common worldwide and is the most common intestinal protozoan parasite in the Western world. The majority of infected individuals remain asymptomatic but it can cause diarrhea that is usually mild but can be severe.

• Question 320:

  A 52-year- oldwoman has had rheumatoid arthritis for many years. She now comes to you complaining of the development in the past few months of redness, burning, and itching of her eyes and a dry mouth, making swallowing difficult. This newly developing condition gives the patient a greatly increased risk for which of the following?

  A. esophageal carcinoma

  B. leukemia

  C. lymphoma

  D. melanoma

  E. pleomorphic adenoma

  Correct Answer: C

  Sjögren syndrome is an autoimmune disease in which there is immune-mediated destruction of lacrimal and salivary gland epithelium leading to diminished secretion by these organs. This disease may occur as a primary disorder or more commonly secondary to another autoimmune disorder, such as rheumatoid arthritis, as seen in this patient. One of the long-term risks for Sjögren syndrome is a 40- fold increase in malignant lymphoma. The development of esophageal carcinoma (choice A) is associated with alcohol use, smoking, Barrett metaplasia, and Epstein-Barr virus infections. Chronic Sjögren syndrome is not known to cause an increased incidence of leukemia (choice B). Melanoma (choice D) is a malignancy of melanocytes unrelated to Sjögren syndrome. Pleomorphic adenoma (choice E) is a benign salivary gland tumor composed of both neoplastic epithelium and stroma. Its occurrence is not associated with Sjögren syndrome.