USMLE USMLE-STEP-1 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-1 Online Questions & Answers

• Question 161:

  A 25-year-old man is admitted to the hospital after coming to the doctor carrying a bottle containing bloody urine. All tests were negative, and he was observed stealing a test tube of blood from the laboratory technician's cart. Which of the following is the most likely diagnosis?

  A. antisocial personality disorder
  B. factitious disorder
  C. malingering
  D. schizophrenia
  E. somatization disorder
  B. factitious disorder

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  Explanation

  Section: Behavioral Science and Biostatics The essential feature of factitious disorder is the intentional production of physical signs or symptoms in the absence of an external incentive as a motivation. If there is an external incentive for fabricating an illness, then malingering is diagnosed (choice C). Antisocial personality disorder (choice A) requires a pattern of antisocial behavior. Somatization disorder (choice E) is characterized by multiple physical symptoms that are not explained by tissue damage. Schizophrenia (choice D) is incorrect because there is no evidence of psychotic symptoms even though the behavior may be bizarre.

• Question 162:

  A renal calculus (kidney stone) passing from the renal pelvis into the ureter causes excessive distention and severe ureteric colic. During development in the embryo, the ureter arose from which of the following?

  A. mesonephric duct
  B. metanephric diverticulum
  C. metanephric mass of intermediate mesoderm
  D. paramesonephric duct
  E. pronephric duct
  B. metanephric diverticulum

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  Explanation

  Section: Anatomy The metanephric diverticulum or ureteric bud gives rise to the ureter, renal pelvis, calices, and collecting tubules. The metanephric mass of intermediate mesoderm (choice C) gives rise to the nephrons in the kidney. The mesonephric and paramesonephric ducts (choices Aand D) play essential roles in the development of the male and female reproductive system, respectively. The pronephric duct (choice E) is derived from the transitory, nonfunctional first set of kidneys or pronephroi and does not contribute to the development of the ureter.

• Question 163:

  The inability to rapidly synthesize DNA during the process of erythrocyte maturation leads to abnormally enlarged erythrocytes. This disorder is referred to as macrocytic anemia and is caused by a deficiency in which of the following vitamins?

  A. ascorbate
  B. biotin
  C. folate
  D. niacin
  E. thiamine
  C. folate

• Question 164:

  Which of the following antiviral drugs is correctly associated with the appropriate primary toxicity?

  A. amantadine--neutropenia
  B. didanosine--pancreatitis
  C. ribavirin--hepatitis
  D. ritonavir--hemolytic anemia
  E. zidovudine--CNS stimulation, GI complaints
  B. didanosine--pancreatitis

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  Explanation

  Section: Pharmacology Didanosine causes pancreatitis in a significant number of patients treated for AIDS. Amantadine (choice A) is used in the prevention and treatment of influenza and causes CNS stimulation and light headedness. Ribavirin (choice C) is used for the treatment of respiratory syncytial virus in infants and causes dose- dependent hemolytic anemia in about 10% of patients. Ritonavir (choice D), a protease inhibitor used in AIDS, causes hepatitis. Zidovudine (choice E), another drug used in AIDS, causes neutropenia as its primary doselimiting effect.

• Question 165:

  A 14-year-old boy is referred to you for nasal obstruction and frequent nosebleeds. Which of the following is the most likely diagnosis?

  A. inverted papilloma
  B. juvenile angiofibroma
  C. nasal polyps
  D. nasopharyngeal carcinoma
  E. wegener granulomatosis
  B. juvenile angiofibroma

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  Explanation

  Section: Pathology and Path physiology Juvenile angiofibroma is a very vascular tumor originating in the nasopharynx that is typically found in teenage boys and young adult males. It may lead to obstruction and, because of its vascularity, it is a frequent cause of epistaxis. It should be suspected in any teenage boy with frequent epistaxis. Inverted papilloma (choice A) is a benign tumor but is aggressive locally and can erode into surrounding structures. Rather than having an exophytic growth pattern, it grows down (thus inverted) into other structures and may be difficult to excise completely. It can cause unilateral obstruction and occasionally epistaxis but is generally seen in an older age group (50s). Nasal polyps (choice C) are not tumors but edematous growths commonly found in patients with allergic rhinitis. They produce chronic nasal obstruction and a gradual loss of olfaction. Nasopharyngeal carcinoma (choice D) is associated with Epstein-Barr virus and is another potential cause of obstruction and hemorrhage but again is seen in older patients. Wegener granulomatosis (choice E) is a necrotizing granulomatous vasculitis involving the nose sinuses, lungs, and kidneys. It occurs most frequently in the fifth and sixth decades.

• Question 166:

  Exhibit:

  

  The graph in below figure shows the static pressurevolume curve of a patient's lung (solid line). The broken line indicates the pressurevolume curve of a normal person for comparison. What is the approximate lung compliance of this patient over the volume range from 1 to 7 L?

  

  A. A
  B. B
  C. C
  D. D
  E. E
  C. C

• Question 167:

  A family reports that their mother's mental status has been deteriorating for the past several years, during which time she has had episodes of transient weaknesses of the arms and legs. Which of the following is the most likely diagnosis?

  A. Alzheimer's disease
  B. Korsakoff syndrome
  C. multi-infarct dementia
  D. old age
  E. vitamin deficiency
  C. multi-infarct dementia

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  Explanation

  Section: Behavioral Science and Biostatics Multi-infarct dementia is caused by repeated cerebrovascular ischemia, indicated in this case by periods of transient paralysis. Alzheimer's disease (choice A) is the most common primary dementia in the elderly. Old age (choice D) alone is no cause for dementia. Korsakoff syndrome (choice B), which is characterized by confabulation, is associated with alcohol withdrawal and thiamine deficiency (choice E). There is no evidence of either in this case.

• Question 168:

  Which of the following is characterized by an absence of lymphoid follicles and germinal centers?

  A. axillary lymph node
  B. Peyer's patches
  C. pharyngeal tonsil
  D. spleen
  E. thymus
  E. thymus

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  Explanation

  Section: Anatomy The thymus provides for development of new T lymphocytes in an environment shielded from foreign antigens. Like bone marrow, the thymus is a primary lymphoid organ, and not a site of reactions to foreign antigens. Lymphoid follicles are sites of B lymphocyte proliferation in response to antigen stimulation. These occur in the lymph nodes (choice A), Peyer's patches (choice B), tonsils (choice C), and white pulp of the spleen (choice D).

• Question 169:

  Metformin is one of the most prescribed hypoglycemia-inducing drugs in the treatment of Type II diabetes. One of the effects of metformin is a reduction in adipose tissue lipolysis, which is effected via the activation of AMP-activated kinase (AMPK). Which of the following actions of AMPK explains the adipose tissue benefits of metformin?

  A. activation of ACC
  B. activation of FAS
  C. inhibition of hormone-sensitive lipase
  D. inhibition of mammalian target of rapamycin (mTOR)
  E. inhibition of 6-PFK-2
  C. inhibition of hormone-sensitive lipase

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  Explanation

  Section: Biochemistry AMP-activated protein kinase (AMPK) was first discovered as an activity that inhibited preparations of ACC and 3-hydroxy-3-methylglutaryl- CoA reductase (HMG-CoA reductase, HMGR) and was induced by AMP. AMPK induces a cascade of events within cells in response to the ever changing energy charge of the cell. The role of AMPK in regulating cellular energy charge places this enzyme at a central control point in maintaining energy homeostasis (see below figure). Once activated, AMPK- ediated phosphorylation events switch cells from active ATP consumption (e.g., fatty acid and cholesterol biosynthesis) to active ATP production (e.g., fatty acid and glucose oxidation). Other important activities attributable to AMPK are regulation of insulin synthesis and secretion in pancreatic islet beta-cells. As shown in

  

  AMPK inhibits (not activates) both ACC (choice A) and FAS (choice B). Activation (not inhibition) of PFK-2 (choice E) occurs in response to AMPK. Although AMPK does indeed inhibit mTOR (choice D), this inhibition does not have any influence on adipose tissue lipolysis.

• Question 170:

  A 42-year-old woman had a catheter placed in her urethra. One week later she is experiencing suprapubic flank pain with urinary urgency and frequency. She has also chills and fever. After examining the patient and evaluating the sediment of her centrifuged urine, she is informed by her physician that she has acute ascending pyelonephritis. If the diagnosis is accurate and the patient's urine is cultured, which of the following organisms will most likely be isolated?

  A. Clostridium difficile
  B. Escherichia coli with pili
  C. Pseudomonas aeruginosa
  D. Staphylococcus aureus
  E. streptococci--group B
  B. Escherichia coli with pili

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  Explanation

  Section: Microbiology/Immunology Piliated strains of E. coli move up the urethra to infect the bladder and kidney. Infections of the kidney cause pyelonephritis. The vast majority of cases of bacterial pyelonephritis, cystitis, and other urinary tract infections are caused by E. coli. Introduction of catheters into the urethra has been associated with the occurrence of urinary tract infections. C. difficile is the cause of pseudomembranous colitis (choice A). S. aureus is usually the cause of boils, skin sepsis, postoperative wound infections, scalded skin syndrome, food-borne infection, septicemia, endocarditis, toxic shock syndrome, osteomyelitis, and pneumonia (choice D). P. aeruginosa is usually the cause of infections of skin and burns. It is also the major pathogen in cystic fibrosis, and can cause urinary infections, but not as commonly as E. coli (choice C). Group B streptococci (choice E) are usual vaginal flora, not pathogenic to the host but may be opportunistic to newborns.