USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 621:

  A newborn infant requires repeated resuscitation in the delivery room because of failure to breathe and cyanosis. During spells of crying, which appear to alleviate the cyanosis, his breath and heart sounds are normal, as is direct laryngoscopy. Vigorous respiratory movements appear ineffectual. Immediate management of this infant consists of which of the following?

  A. obtaining a chest x-ray
  B. obtaining an electrocardiogram (ECG)
  C. arterial blood gas determinations
  D. inserting an oropharyngeal airway
  E. administration of naloxone
  D. inserting an oropharyngeal airway

  ---

  Explanation

  The presence of a congenital membranous or bony septum between the nose and pharynx is called choanal atresia. Most newborns are obligatory nose breathers and breathe effectively only through their noses. Therefore, if choanal obstruction is unilateral, breathing difficulty may not occur until the first respiratory infection. On the other hand, those newborns with bilateral atresia who are also obligatory nose breathers will make vigorous attempts to inspire with sucking in of their lips, or may promptly become apneic and cyanotic, requiring resuscitation. Those who are able to mouth breathe may have difficulty when feeding or manifest persistent mouth breathing and cyanosis that is relieved by crying.

  Treatment consists of surgical correction.

• Question 622:

  A28-year-old woman with a 7-year history of chronic undifferentiated schizophrenia is hospitalized for an exacerbation of her schizophrenia, with an increase in auditory hallucinations. She has also developed the delusion that she is controlled by aliens from Mars. She has always been very sensitive to the extrapyramidal side effects (EPS) of antipsychotic medications.

  Which of the following is an extrapyramidal side effect of antipsychotic medications most likely to be seen in the first few days of treatment with typical neuroleptic antipsychotics?

  A. pill-rolling tremor of the hands
  B. severe restlessness of the arms and legs
  C. involuntary lip smacking
  D. muscle spasm in the neck
  E. masked facies
  D. muscle spasm in the neck

  ---

  Explanation

  Typical neuroleptic antipsychotic medications frequently cause unpleasant side effects, which occur at various times during treatment. The extrapyramidal side effect most likely to occur in the first few days of treatment is an acute dystonia, such as a muscle spasm in the neck. A pill-rolling tremor of the hands and masked facies are signs of Parkinsonian EPS, which tend to have their onset several weeks after treatment is begun; whereas severe restlessness of the arms and legs is caused by an unpleasant sensation called "akathisia," which also tends to have its onset several weeks after treatment is begun. Involuntary lip smacking is a sign of tardive dyskinesia, a sometimes irreversible motor syndrome that tends to occur after months or years of treatment with typical antipsychotics. Anticholinergic medications such as benztropine are effective in treating dystonias and pill-rolling tremors. Propranolol is effective in treating akathisia. Haldoperidol would worsen EPS. Dantrolene uncouples muscle contractions and is used occasionally in severe NMS. L-Dopa would decrease the Parkinsonian EPS, but would worsen the psychosis and therefore is not used. Fluoxetine is an SSRI.

• Question 623:

  A 30-year-old woman comes to your office for evaluation of fatigue and shortness of breath on exertion. Past medical history is unremarkable. Physical examination is remarkable only for mild pallor. Lung and cardiovascular examination are normal. Laboratory tests show a hematocrit of 28 with a mean corpuscular volume of 72. WBC count and platelet count are normal. On taking further history from the patient, which of the following patient questions would most likely confirm a diagnosis?

  A. What is your family history of colon cancer?
  B. What is your family history of heart disease?
  C. How much alcohol do you drink?
  D. Do you have attacks of pain in your joints?
  E. How heavy are your menstrual periods?
  E. How heavy are your menstrual periods?

  ---

  Explanation

  Iron-deficiency anemia characteristically is a hypochromic, microcytic anemia. Causes of iron- deficiency anemia include menstrual loss, inadequate diet, malabsorption, chronic inflammation, and chronic blood loss. Colon cancer could lead to chronic blood loss and irondeficiency anemia. This, however, would be very uncommon in a young patient without a family history of colon cancer.

  Alcohol causes a macrocytic anemia.

• Question 624:

  A 78-year-old woman comes to your primary care office practice with her son who is concerned about changes in her mood. She is less interested in going out to dinner and does not want to visit family or friends. Her language skills seem to have deteriorated over the last few years and her memory is not as sharp. Her gait and motor strength are normal. Which of the following is the most likely diagnosis?

  A. Parkinson's disease
  B. anxiety disorder
  C. meningioma
  D. Alzheimer's disease
  E. dysthymia
  D. Alzheimer's disease

  ---

  Explanation

  Classic features of Alzheimer's syndrome include amnestic memory impairment, deterioration of language, and visuospatial deficits. Gait disturbances and motor and sensory changes are uncommon until late phases of the syndrome. Mood change and apathy are commonly seen in early stages of Alzheimer's syndrome and typically continue for the duration of the disease. Psychotic features may be seen in middle and late phases of the syndrome.

• Question 625:

  During a routine checkup, a 45-year-old executive is found to have hypercalcemia. Subsequent workup reveals elevated parathormone, decreased phosphorus, elevated chloride, and normal blood urea nitrogen (BUN), and creatinine in serum. Urinary calcium is above normal levels. What is the most likely etiology?

  A. multiple myeloma
  B. primary hyperparathyroidism
  C. hypervitaminosis D
  D. sarcoidosis
  E. milk alkali syndrome
  B. primary hyperparathyroidism

  ---

  Explanation

  Primary hyperparathyroidism is characterized by hypercalcemia, hypophosphatemia, hyperchloremia, increased urinary calcium excretion, and an increase in serum parathormone level. Multiple myeloma is associated with hypercalcemia when there are many lytic lesions. Chronic ingestion of 50100 times the normal requirement of vitamin D is required to produce hypercalcemia in normal people, so hypervitaminosis D is rare and parathormone levels would be suppressed. With milk alkali syndrome, which is caused by excess ingestion of calcium and absorbable antacids, parathormone levels would also be suppressed. In sarcoidosis, about 10% of patients have hypercalcemia attributable to increased intestinal absorption of calcium and increased production of 1,25(OH)2D.

• Question 626:

  A 27-year-old woman with amenorrhea of 6 months' duration relates a 4-month growth of thick, black hair on her face, chest, and abdomen. She takes no medications with androgenic effects. Her family history is negative for hirsutism. The hirsutism is confirmed by your examination. Her pelvic examination is normal other than a mild male pubic hair pattern. Your evaluation of this hirsute, amenorrheic woman is normal except for a significantly increased serum DHEAS concentration. Additional history discloses that her menses have always been somewhat irregular since menarche at age 10 years. She has a 23-year-old sister with irregular menstrual intervals and hirsutism to a lesser degree. This patient has a blood pressure of 96/64 mmHg. Which of the following is the most likely diagnosis?

  A. polycystic ovary syndrome
  B. 21-hydroxylase deficiency
  C. 11-hydroxylase deficiency
  D. 17-hydroxylase deficiency
  E. Sertoli-Leydig cell tumor
  B. 21-hydroxylase deficiency

  ---

  Explanation

  A history of irregular menses from menarche suggests a functional disorder, such as polycystic ovary syndrome or attenuated adrenal hyperplasia attributable to an inherited enzyme deficiency. The absence of a unilateral ovarian mass on pelvic examination, the positive family history, and the early menarche favor a diagnosis of attenuated adrenal hyperplasia over that of a virilizing ovarian tumor. Women with 17- hydroxylase deficiency or 11-hydroxylase deficiency are hypertensive. Women with 17- hydroxylase deficiency are also sexually infantile, not hirsute, because they are unable to produce androgens or estrogens in normal amounts. Women with 21-hydroxylase deficiency may have salt wasting and hypotension if the enzyme deficiency is sufficiently severe.

• Question 627:

  A 65-year-old diabetic man presents to the emergency department with a history of a penetrating wound to his buttock by a wooden stump while working in his garden 24 hours earlier. On examination, he is febrile, the tissue around the wound is violaceous in color, and several bullae and crepitus are noted in the buttock. The drainage from the wound is foul smelling, watery, and grayish in appearance.

  The optimal treatment for this patient would include which of the following?

  A. high-dose IV penicillin G and broadspectrum antibiotics
  B. high-dose IV penicillin G, broadspectrum antibiotics, and local wound care with unroofing of bullae and culture of wound drainage
  C. high-dose IV penicillin G, broadspectrum antibiotics, with surgical debridement only if and when there is no improvement with antibiotics
  D. radical surgical debridement
  E. high-dose IV penicillin G, broadspectrum antibiotics, radical surgical debridement, and hyperbaric oxygen therapy
  E. high-dose IV penicillin G, broadspectrum antibiotics, radical surgical debridement, and hyperbaric oxygen therapy

  ---

  Explanation

  This patient presents with a rapidly progressive, necrotizing soft-tissue infection. The skin edema, purple hue, bullae, water drainage, and crepitus are classic findings in clostridial infections. Although culture of the wound drainage may be confirmatory, the diagnosis should be suspected on a clinical basis. Antibiotics alone are insufficient therapy. The mainstay of therapy is radical surgical debridement of devitalized tissues, in conjunction with high-dose IV antibiotics.

  Hyperbaric oxygen therapy may facilitate recovery.

• Question 628:

  A 2-week-old Caucasian male presents with constipation since birth. He was born full term via a normal vaginal delivery. He did not pass meconium till his 3rd day of life, after he was given a glycerin suppository. He has since stooled every 34 days, only with the help of a suppository. The stools are pellet like. He has had increasing abdominal distention. On rectal examination, tone appears normal and the ampulla contains no stool.

  Which of the following is the most likely cause?

  A. cystic fibrosis
  B. Hirschprung disease
  C. anal stenosis
  D. functional constipation
  E. hypothyroidism
  B. Hirschprung disease

  ---

  Explanation

  Hirschprung disease or congenital aganglionic megacolon is the most common cause of lower intestinal obstruction in neonates. Incidence is 1/5000 live births; males are four times as likely to be affected. Initial presentation is with delayed passage of meconium. Failure to pass stools leads to dilation of proximal bowel and abdominal distention. Diagnosis is by barium enema which reveals a small-caliber rectum with transition in the rectosigmoid to a dilated, obstructed proximal colon. Diagnosis is confirmed by biopsy. Meconium plugs and meconium ileus are often found in cystic fibrosis, which should be excluded. Anal stenosis may be diagnosed by rectal examination or endoscopy. Functional constipation usually presents in children older than 2 years. There may be some abdominal distention; anal tone is usually normal, and the rectal ampulla is often full of stool. Congenital hypothyroidism may present with constipation; neonatal screening tests usually allow early diagnosis. Other features include feeding difficulties, prolonged jaundice, sluggishness, a large abdomen with umbilical hernia, subnormal body temperature, myxedema, and developmental delay.

• Question 629:

  From the below the clinical indications, choose an option for use of immune globulin (IG) in Hepatitis B prophylaxis

  A. indicated
  B. not proven effective
  C. not routinely indicated
  D. contraindicated
  E. compulsory
  B. not proven effective

  ---

  Explanation

  IG given before exposure or within 14 days of exposure is 7585% effective in preventing symptomatic illness from hepatitis A. IG is produced from the plasma of normal adults and does not contain sufficient antibody to prevent hepatitis B infection. Hepatitis B immune globulin (HBIG) is prepared from plasma known to contain high antibody titers for hepatitis B surface antigen (HBsAg) and is specific for hepatitis B. Given immediately postexposure, and again 1 month later, it has a combined efficacy of about 75% in the prevention of hepatitis B. Postexposure IG has not been found effective in the prevention of hepatitis C infection; on the other hand, treatment of early hepatitis C infection is possible, and thus it is important to monitor exposed individuals to determine whether infection occurs. IG administered to individuals exposed to measles infection who are susceptible to the disease has been shown to be effective if given within 6 days of exposure.

  Recent use of IG is a contraindication to immunization with rubella vaccine. IG is not very effective at preventing in utero infection with rubella, and infants with congenital rubella syndrome have been born to women given IG shortly after exposure. IG is not routinely indicated, as it is indicated only if abortion is not elected.

• Question 630:

  A dentist asks you to evaluate a 42-year-old woman before tooth extraction. Which of the following would prompt you to prescribe prophylactic antibiotics?

  A. midsystolic click at the left sternal border
  B. insulin-dependent diabetes
  C. a prior history of infective endocarditis
  D. a history of congestive heart failure
  E. S4 gallop
  C. a prior history of infective endocarditis

  ---

  Explanation

  Guidelines for antibiotic prophylaxis of infective endocarditis (IE) underwent a major revision in 2007. Prophylaxis is now only recommended for those patients at highest risk of IE including patients with a prosthetic valve, history of IE, cardiac transplant patients that develop valvulopathy, cyanotic congenital heart disease that remains unrepaired, cyanotic congenital heart disease that has been repaired with a prosthesis during the first 6 months after the procedure or if a defect remains at the site of the prosthesis after 6 months. Congestive heart failure, an S4 gallop, and diabetes do not increase risk. Recommended antibiotic coverage for high-risk patients before dental procedures is amoxicillin 2 g PO 1 hour before the procedures. Penicillin- allergic patients can receive clarithromycin, cephalexin, cefadroxil, or clindamycin as prophylaxis. Streptococci and S. aureus are responsible for the majority of community- acquired native valve endocarditis cases.

  In IV drug abusers, S. aureus is responsible for more than 50% of cases, and Candida and Pseudomonas for about 6% each. Patients with prior endocarditis are at high risk. Bacterial endocarditis carries a mortality rate of about 25%, and prevention is of paramount importance. In S. aureus endocarditis in injection drug users, mortality is only 1015%. As many as 40% of cases occur without underlying heart disease. VSD, patent ductus arteriosus, and tetralogy of Fallot are most commonly associated;

  whereas, ASD is rarely a predisposing factor.