USMLE USMLE-STEP-3 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 471:

  Apatient you see routinely in the clinic has elevated liver function tests. ALT is 89, AST is 75, and the total bilirubin and alkaline phosphatase are normal. The patient has no past history of hepatitis, taking medications, or excessive drinking. You order hepatitis serologies. The results are as follows: Positive:

  HBsAg and anti-HBc. Negative: anti-HBs, anti-HBc IgM, anti-HAV, and anti-HCV

  What is your interpretation?

  A. The patient has acute hepatitis B.
  B. The patient needs a test for IgM antibody to hepatitis A virus to rule out acute hepatitis A.
  C. The patient needs a test for hepatitis C antigen to exclude acute hepatitis C.
  D. The patient has chronic hepatitis B.
  E. If the patient had a negative test for HBsAg, they could be infected with hepatitis delta.
  D. The patient has chronic hepatitis B.

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  Explanation

  This patient has chronic hepatitis B. The different serologic studies for hepatitis B are shown in two figures below. The patient does not have acute hepatitis B because the IgM antibody to hepatitis B core is negative, and the total antibody to hepatitis B core is positive. Antibody to hepatitis B core occurs prior to the development of antibody to hepatitis B surface. IgM is found in acute infections; primarily IgG is seen in chronic infections.

  

  

  The presence of antibody to hepatitis B core with a positive hepatitis B surface antigen is indicative of chronic infection. Delta hepatitis infection requires the hepatitis B surface antigen. Delta hepatitis can occur concurrently with acute hepatitis B infection or later in the setting of chronic hepatitis B infection. There is no test for hepatitis C antigen. This is not a presentation of acute hepatitis A, which usually has very high transaminases. The antibody to hepatitis A virus occurs after 1 month and is associated with high transaminases Hepatitis Avaccine is indicated for patients with chronic liver disease. If this patient had hepatitis C, then hepatitis B vaccine would also

  

  

  

  be indicated. Hepatitis B vaccine is essentially hepatitis B surface antigen that causes the production of hepatitis B surface antibody. Since this patient has hepatitis B surface antigen already, choice C would be incorrect. Verifying the diagnosis with a qualitative hepatitis B viral load is not necessary. A quantitative hepatitis B viral load might be useful to evaluate for potential antiviral therapy. The only reason hepatitis Awould be recommended for the patient's spouse would be if the patient had acute hepatitis

  A. Investigating for other causes of hepatitis is not necessary as the diagnosis of chronic hepatitis B is already established.

  If the patient was found to be HBeAg positive, he would be considered highly infectious for the spread of hepatitis

  B. Hepatitis Be antigen is the DNA polymerase that shows active replication of the hepatitis B virion. These patients are 100 times more infectious than those lacking the hepatitis Be antigen. The window period is a situation where a patient is just recovering from hepatitis

  B. Hepatitis Bs antigen is negative and the antibody to hepatitis Bs has not been developed. The diagnosis is made by antibody to hepatitis B core. This is seen in Figure 1-6. Any patient who is hepatitis B surface antigen positive is at risk for delta hepatitis. This patient would be at risk for delta hepatitis by virtue of having a positive hepatitis B surface antigen. There is no level of transaminases, even normal transaminases, which would preclude antiviral therapy. The level of viral production indicated by the hepatitis B quantitative viral load, along with an assessment of the underlying liver pathology, is the best indication of need for treatment. As mentioned earlier, the antibody to hepatitis B would show the patient is less infectious and likely have a lower viral load.

• Question 472:

  A22-year-old male presents to an acute care clinic in order to have two genital lesions evaluated. He first noticed the lesions about 2 weeks ago, but delayed seeking medical care because he believed they were harmless due to the lack of any discomfort. He states that he does engage in unprotected sexual intercourse, with the most recent time being 1 month ago. On examination, the glans penis features two distinct nontender papules with elevated edges surrounding ulcerated craters. They each measure 1 cm in diameter. There is also nontender bilateral inguinal lymphadenopathy. Six hours after treating this patient, he calls your office with complaints of new-onset headache, myalgia, and malaise. He also states that he felt feverish immediately prior to calling and measured his temperature, which was 99.8. Which of th e following is most appropriate at this time?

  A. Advise transport to the nearest ED for immediate evaluation.
  B. Advise use of acetaminophen and provide reassurance.
  C. Advise immediate use of Benadryl and then have the patient go to the nearest ED.
  D. Start treatment with levaquin.
  E. Start treatment with oral corticosteroids.
  B. Advise use of acetaminophen and provide reassurance.

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  Explanation

  This patient's presentation is consistent with primary syphilis. Primary syphilis manifests itself usually in the form of solitary or multiple raised, firm papules which eventually erode to form ulcerative craters with raised, indurated margins surrounding the centralized ulcer. These lesions, called chancres, most commonly involve the glans penis in males and the vulva or cervix in females, although they may appear rarely in other areas. Syphilis is caused by the spirochete, T. pallidum, which can be visualized by darkfield microscopy, by silver stain, or by fluorescent antibody microscopy. There is an incubation period of approximately 3 weeks separating the time of initial exposure to T. pallidum and the time of chancre formation. Syphilis is characterized by the presence of latent stages in which there are no signs of clinical disease present. Penicillin is the drug of choice for the treatment of syphilis. In addition to treating patients with diagnosed syphilis, it is recommended that treatment also be administered to all sexual contacts of the past 90 days. It has been demonstrated that up to 30% of asymptomatic sexual contacts of patients with infectious lesions within the past 30 days go on to develop syphilis if left untreated. If left untreated, patients may ultimately develop tertiary syphilis characterized by significant destructive neurologic and cardiovascular symptoms. The mortality rate for untreated tertiary syphilis is approximately 20%.

  Cephalosporins and penicillin antibiotics act by interfering with the late stages of bacterial cell wall synthesis, although the precise biochemical reactions are not entirely understood. Peptidoglycan provides mechanical stability to the cell wall because of its high degree of cross-linking with alternating amino pyranoside sugar residues (N-acetylglucosamine and N-acetylmuramic acid). The completion of the cross- linking occurs by the action of the enzyme transpeptidase. This transpeptidase reaction, in which the terminal glycine residue of the pentaglycine bridge is joined to the fourth residue of the pentapeptide (D- alanine) thereby releasing the fifth residue (D-alanine), is inhibited by beta- lactams.

• Question 473:

  A28-year-old male, well known to your clinic, presents for management of swelling, pain, and tenderness that has developed in his left ankle and right knee. It has persisted for 1 month. Your patient reports that he developed severe diarrhea after a picnic 1 month prior to the onset of his arthritis. During the interval between the diarrhea and onset of arthritis, he developed a "pink eye" that lasted for 4 days. He denies any symptoms of back pain or stiffness. You remember that he was treated with ceftriaxone and doxycycline for gonorrhea 2 years ago, which he acquired from sexual activity with multiple partners. Since that time, he has been in a monogamous relationship with his wife and has not had any genitourinary symptoms. He promises that he has been faithful to his wife and has not engaged in unprotected sexual activity outside his marriage. His physical examination is notable for a swollen left ankle, swollen right knee, and the absence of penile discharge or any skin lesions. Which of the following is the most likely diagnosis?

  A. pseudogout
  B. gout
  C. reactive arthritis
  D. resistant gonococcal arthritis
  E. ankylosing spondylitis
  C. reactive arthritis

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  Explanation

  Reactive arthritis consists of a triad of nonspecific urethritis, conjunctivitis, and asymmetric arthritis, usually involving the large joints of the lower extremities. Genitourinary causes of reactive arthritis include Chlamydia or Ureaplasma. GI infections due to Salmonella, Shigella, Yersinia, Klebsiella, and Campylobacter can also cause reactive arthritis. Gout attacks are typically monoarticular and begin abruptly with the affected joint being exquisitely painful, warm, red, and swollen. These attacks often spontaneously resolve in 310 days. While the symptoms from pseudogout may mimic those of gout, they tend to be less painful and take longer to reach peak intensity. Gonococcal arthritis is seen more often in females, is associated with migratory arthralgia, tends to favor the upper limbs and knees and may be associated with cutaneous lesions (pustules). The absence of attacks and joint distribution makes gout and pseudogout less likely. The history of conjunctivitis and association with diarrhea makes the diagnosis of reactive arthritis more likely than resistant gonococcal arthritis. His clinical symptoms do not suggest ankylosing spondylitis, although if he was HLA-B27 positive he would be at increased risk of developing spondylitis. This patient has the classic symptoms and exposure risk (GI infection) to suggest reactive arthritis. For the articular symptoms, reduction of inflammation and restoration of function can be achieved with nonsteroidal antiinflammatories alone. A sufficient number of patients with reactive arthritis will not be HLA-B27 positive, thus rendering this test useless as a screening test. However, it may be useful when the clinical picture is incomplete (such as absence of antecedent infection or lack of extraarticular features). Once an antecedent infection has triggered reactive arthritis, it is unlikely that antibiotics will affect the course of the illness (except in the case of chlamydiaassociated urogenital disease where a trial of prolonged antibiotic therapy may be reasonable).

  Systemic corticosteroids are usually ineffective in reactive arthritis, but may be tried for resistant disease or conditions such as AIDS in which cytotoxic therapy is contraindicated. Given the absence of skin lesions, penile discharge, or urogenital symptoms, one would be hard-pressed to challenge the patient's statement that he has not engaged in unprotected sex at the risk of jeopardizing the physicianpatient relationship. Reactive arthritis may be the first manifestation of HIV infection. Therefore, HIV antibody status should be determined when the appropriate risk factors and/or clinical features are present. As mentioned previously, systemic steroids are usually ineffective for reactive arthritis and, with the possibility of joint infection, would necessitate ruling out infection by arthrocentesis of the affected joints. Joint infection cannot be ruled out based on his presentation, and joint sepsis must be excluded prior to corticosteroid injection. The clinical presentation is classic for reactive arthritis, and the absence of systemic symptoms makes the likelihood of disseminated bacterial infection low. Indomethacin, at a dose of 150200 mg/day, is the prototypic NSAID medication for treatment of reactive arthritis. Doses higher than this are associated with significant GI complications and do not improve efficacy in a patient resistant to the standard dose. In the event that the patient does not respond to 200 mg of indomethacin or alternative NSAIDs, disease- modifying antirheumatic drugs (DMARD) such as methotrexate, azathioprine, or sulfasalazine may be used, provided that HIV test results are negative, as these immunosuppressants have been reported to precipitate the onset of AIDS in HIV-positive patients.

• Question 474:

  A42-year-old male with extensive Crohn's disease undergoes a near complete resection of the ileum. Adeficiency of which of the following vitamin is likely to result?

  A. niacin
  B. thiamine
  C. vitamin B12
  D. vitamin C
  E. vitamin B6
  C. vitamin B12

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  Explanation

  The distal small bowel (ileum) is the site of absorption of fat-soluble vitamins (vitamins A, D, E, and K) as well as vitamin B12. Vitamin B12 binds with intrinsic factor, a glycoprotein secreted from parietal cells of the gastric fundus and body. Specific receptors in the terminal ileum take up the B12 intrinsic factor complex. Vitamin B12 deficiency leads to megaloblastic anemia. The patient will require monthly vitamin B12 injections

• Question 475:

  A newborn male is brought to you in the neonatal intensive care unit (NICU). On physical examination, you notice that the infant has deficient abdominal musculature and undescended testes. Your suspicion is high for a certain condition.

  You presumptively diagnose the child with which of the following?

  A. VATER association
  B. Cushing's triad
  C. Potter's syndrome
  D. Jones criteria
  E. Eagle-Barrett syndrome
  E. Eagle-Barrett syndrome

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  Explanation

  The constellation of cryptorchidism, posterior urethral valves, and abnormal abdominal musculature is called Eagle-Barrett syndrome. Another name is prune belly syndrome. The greatest morbidity comes from the poor amniotic fluid production, due to bladder outlet obstruction, with a resulting pulmonary hypoplasia. Cushing's triad are hypertension, bradycardia, and widened pulse pressure. This is seen as terminal findings associated with increased intracranial pressure. VATER association has multiple anomalies, none of which are the three mentioned. VATER is a mnemonic which stands for Vertebral anomalies, Anal atresia (imperforate), Tracheo-Esophageal fistula, and Renal anomalies (the R also indicated Radial anomalies). It is sometimes referred to as VACTERL association in which the C indicates Cardiac anomalies with the L indicating Limb anomalies. Potter's syndrome is bilateral renal agenesis. This condition is fatal, due to marked pulmonary hypoplasia. The Jones criteria are used in the diagnosis of ARF.

• Question 476:

  A15-year-old female presents to the emergency room (ER) with acute onset right lower quadrant pain and nausea. She recently became sexually active and is "in the middle" of her menstrual cycle. Physical examination is notable for generalized guarding, rebound, and 8/10 pain in both lower quadrants. A pelvic examination shows no vaginal discharge, a normal appearing cervix, and general pelvic tenderness, but the examination is limited by the patient's guarding. Her complete blood count is notable for a borderline elevated white blood cell (WBC) count, and a urinary -hCG is negative. Pelvic ultrasound shows a 2-cm simple appearing cyst on the right ovary and a mild amount of fluid in the cul-de-sac. Acomputed tomographic (CT) scan cannot definitively visualize the appendix, confirms the presence of a 2-cm cystic structure in the right ovary, and otherwise notes normal anatomy.

  Which of the following is the most appropriate next step?

  A. diagnostic laparoscopy
  B. pelvic MRI
  C. intravenous antibiotics
  D. admission for serial physical examinations and pain control
  E. discharge home on oral antibiotics
  A. diagnostic laparoscopy

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  Explanation

  Acute pelvic pain is a difficult diagnostic dilemma. An acute abdomen can result from appendicitis, ovarian torsion, ruptured ovarian cyst, ectopic pregnancy, PID, diverticular abscess, and other causes. Misdiagnosis of PID is common and the most likely diagnosis confused with PID is appendicitis. In the setting where the etiology of the acute abdomen is not certain, a laparoscopy is indicated both for diagnostic and, in many cases, therapeutic purposes. A pelvic MRI or serial examinations would further delay the diagnosis. In the case of ovarian torsion or appendicitis, rapid diagnosis and treatment is critical to optimize outcomes.

• Question 477:

  In your role as a physician in a community health center, you agree to perform sports preparticipation examinations on students from the local high school. You have several scheduled for today. Your first appointment is with a 16-year-old male who is planning to run on the cross-country team in the Fall and play baseball in the Spring. He reports that one time he "blacked out" while running, but he has never had chest pain while exercising and he is one of the top runners on the team. He has no known medical history, denies alcohol, tobacco, recreational drug, or performance-enhancing drug use. He has a cousin who died at the age of 21 of "some kind of heart disease," although your patient is not sure of any details. On examination, he is healthy appearing and has normal vital signs, with a pulse rate of 72 and a blood pressure of 100/65. Auscultation of his heart reveals no cardiac murmur while he is lying down, a soft systolic murmur when he stands which increases on having the patient perform a Valsalva maneuver. The remainder of his examination is normal

  Appropriate diagnostic testing would include which of the following?

  A. chromosomal analysis
  B. echocardiography
  C. serum calcium measurement
  D. fasting plasma glucose
  E. cervical spine x-rays with flexion and extension views
  B. echocardiography

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  Explanation

  Explanations:

  Primary care physicians are frequently called on to perform preparticipation examinations on young athletes. These types of encounters can be used to serve a number of purposes, including attempting to identify conditions that may adversely affect the athlete during participation, identify conditions that may predispose the athlete to injury, provide anticipatory guidance on high-risk behaviors common to the age group being addressed, and fulfill legal conditions of the institution involved. Fortunately, the rate of sudden death in young athletes is low.

  In those under the age of 35, the most common cause of sudden death is congenital cardiac anomalies. Hypertrophic cardiomyopathy (HCM) is responsible for about onethird of these deaths. Unfortunately, sudden death may be the presenting symptom of HCM. Apersonal or family history of congenital heart disease, symptoms of chest pain or tightness, palpitations, dyspnea, syncope or near-syncope are important. A family history of HCM or unexplained sudden death in someone under the age of 50 is significant as well. The murmur of HCM may not be present in all persons with this disorder.

  To identify the murmur, dynamic auscultation is often necessary. The heart should be auscultated while the patient is lying and then standing. As this murmur is accentuated by maneuvers which reduce cardiac preload, the murmur will get louder when the patient stands or performs a Valsalva maneuver and will diminish as the patient lies or squats. As the patient has the concerning historical point of exertional syncope and a family history of an unexplained, early death along with a characteristic murmur on examination, further evaluation is warranted. In the 26th Bethesda Conference report, the American College of Cardiology recommends that persons with HCM should be restricted from all, except possibly for the least strenuous, athletic activity. In this case, restriction of all athletic activity until the patient can be further evaluated by a cardiologist--preferably one with experience in dealing with the evaluation of athletes--would be the most appropriate option of the choices given.

  Marfan syndrome is a connective tissue disorder that typically affects the eyes, skeletal system, and cardiovascular system. Persons with Marfan syndrome are typically tall and have arm spans that are greater than their height. Signs include long, slender digits, high-arched palates, and pectus deformities of the chest. Lens dislocations in the eye are common. Detecting Marfan syndrome during a preparticipation examination is important because of the occurrence of aortic\ root dilation and the risk of sudden death caused by aortic rupture. The patient in questions 23 and 24 has multiple signs of Marfan syndrome and further evaluation would be indicated. Of the options given, an echocardiogram to evaluate the aortic root and to look for other valvular abnormalities would be indicated. These persons usually require referral to an ophthalmologist as well for a dilated eye examination to evaluate for lens dislocations. Turner syndrome is a syndrome of gonadal dysgenesis, associated with a 45, X karyotype (or another defect of the X chromosome). This syndrome is typically associated with a short stature and multiple anomalies including a webbed neck and "shield" chest. The female athlete triad is a syndrome of disordered eating, amenorrhea, and osteoporosis. It is seen most often in participants in activities that emphasize low body weights, such as gymnastics or ballet. The presence of regular menstrual cycles makes this diagnosis unlikely. Atlantoaxial instability can be associated with Down syndrome.

  Physicians performing preparticipation examinations on someone with Down syndrome must consider performing lateral cervical spine x-rays with flexion and extension views. This patient does not have any of the classic findings of Down syndrome. Similarly, she does not exhibit any of the classic symptoms of type 1 diabetes polydipsia, polyphagia, and polyuria. Performing serum glucose testing would therefore not be indicated. The patient is the most typical type of patient who presents for a preparticipation examination-- the healthy adolescent. This may be the only encounter that a physician will have with an adolescent, especially an adolescent male. It is in this population where a physician can use this encounter to address other age appropriate health maintenance issues. As the patient had a Td booster 3 years ago, another one at this point would not be indicated (although consideration could be given to providing a Tdap). Other vaccinations to consider would be hepatitis B and MMR, if he has not previously been adequately immunized. As he has had two MMR vaccines, he has completed the recommended series. There is no history given regarding hepatitis B vaccination and this would be something to address clinically. A nonjudgmental discussion of sexual behaviors, drug use, alcohol use, and other high-risk behaviors would also be appropriate. Screening athletes who have neither concerning symptoms nor signs with ECGs is not recommended because of the poor predictive values and significant costs involved with mass screening. ECGs should be performed without hesitation in any athlete who has a history, examination finding, or preexisting diagnosis of a potentially high-risk condition. Although some localities may require a urinalysis as part of a preparticipation examination, there is no evidence to recommend universal screening

• Question 478:

  A 14-year-old nulligravid female is brought to the ER by her parents with a 12-hour history of severe, intermittent left lower quadrant pain. She has had nausea and vomiting for the past 2 hours. On history, the patient experienced menarche at age 12 and denies past or current contact with a sexual partner. Her last normal menstrual period was 3 weeks ago. On examination, she is afebrile, pulse 100, BP 110/70, respiratory rate (RR) 20. She is visibly uncomfortable. She has no costovertebral tenderness, has diminished bowel sounds, her abdomen is nondistended, and exhibits rebound and guarding in both lower quadrants. She is unable to tolerate a pelvic examination due to pain. Laboratory values are as follows:

  WBC 13, HCT 39, -hCG (-), UA (-). Apelvic ultrasound shows a normal nonpregnant uterus, normal right adnexa, and an 8-cm left adnexal mass with a 3-cm solid component.

  Which of the following would be the next appropriate step in managing this patient?

  A. abdominal and pelvic CT scan
  B. social work referral for possible sexual abuse
  C. obtain liver enzymes, amylase, and lipase
  D. consultation for immediate surgical intervention
  E. discharge to home with pain medications
  D. consultation for immediate surgical intervention

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  Explanation

  This patient is demonstrating acute peritoneal signs that require surgical intervention. Adding additional testing, either with radiology or more laboratory assessment would not alter the management at this point in time. Although some patients with chronic pelvic pain have a history of sexual or physical abuse, an assessment in the acute emergent setting does not take initial priority. Although ovarian torsion can be enigmatic in its presentation, this patient demonstrates classic signs of intermittent pelvic pain and an ovarian cyst with a solid component. The 8-cm increase in ovarian size is likely due to vascular congestion from occlusion of the blood supply. Early intervention is more likely to result in salvaging viable tissue before the onset of irreversible tissue necrosis. The absence of fever and other GI symptoms, along with a left lower quadrant mass on ultrasound goes against the possibility of appendicitis or pancreatitis. Her pregnancy test is negative which generally excludes an ectopic pregnancy.

• Question 479:

  A 5-year-old girl presents for evaluation of breast development, history of multiple bone fractures, and vaginal bleeding. Physical examination is notable for "caf?au lai"; spots on her skin, tanner stage 2 breasts, and she appears tall for her age. What is the most likely cause of precocious puberty in this child?

  A. acromegaly
  B. McCune-Albright syndrome
  C. ovarian cyst
  D. ingestion of her mother's oral contraceptives
  E. hyperparathyroidism
  B. McCune-Albright syndrome

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  Explanation

  The McCune-Albright syndrome is due to a G-protein mutation in the alpha-subunit that causes constitutive stimulatory activity of the tissues. Affected tissues are autonomously active. McCune- Albright syndrome classically consists of a triad of caf?au lait skin spots, cystic bone lesions (polyostotic fibrous dysplasia), and autonomous endocrine hyperfunction resulting in sexual precocity. Adominant ovarian cyst develops independent of stimulation by gonadotropins and it secretes estradiol, resulting in sexual precocity and skeletal maturity. Therefore, the finding of elevated estradiol levels and suppressed or undetectable gonadotropins is diagnostic. Affected individuals also may have hyperthyroidism, hypercortisolism, pituitary gigantism, or acromegaly.

• Question 480:

  A healthy 38-year-old G4P3003 presents for amniocentesis. The karyotype returns as shown in the Figure.

  What is the diagnosis?

  

  A. Down syndrome
  B. Patau syndrome
  C. Edwards syndrome
  D. Turner syndrome
  E. Klinefelter syndrome
  A. Down syndrome

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  Explanation

  Down syndrome is a trisomy of chromosome 21. It is the most common nonlethal trisomy. Patau syndrome is trisomy 13 and Edwards syndrome is trisomy 18. Turner syndrome is 45 X, a monosomy. Klinefelter syndrome is the presence of an extra X chromosome in a male resulting in 47 X-X-Y. Down syndrome is the most commonly recognized genetic cause of mental retardation. The risk of trisomy 21 is directly related to maternal age as a result of maternal nondisjunction. The risk of having a child with Down syndrome increases in a gradual, linear fashion until about age 30 and increases exponentially thereafter. Women who will be 35 years or older at the time of delivery should be offered chorionic villus sampling or secondtrimester amniocentesis. Women younger than 35 years should be offered maternal serum screening at 1618 weeks of gestation. The maternal serum markers used to screen for trisomy 21 are alpha-fetoprotein, unconjugated estriol, and hCG. The use of ultrasound to estimate gestational age improves the sensitivity and specificity of maternal serum screening.