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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 731:

  A 49-year-old male postal worker presents to your office for the evaluation of a lesion on his left arm. The lesion started about a week ago as a red pustule but has grown and now has a thick black scab. The lesion is painless. A coworker showed the patient a similar appearing lesion that she developed on her arm for which her doctor prescribed an oral antibiotic. Examination reveals a 5 cm circular black eschar with some surrounding vesicles. A Gram stain of fluid drained from a vesicle reveals chains of gram-positive bacilli. Which of the following is characteristic of Varicella (chickenpox) but not smallpox?

  A. The mortality rate is high.
  B. The lesions are commonly on the palms of the hands and soles of the feet.
  C. The pox lesions evolve synchronously.
  D. There is typically a 2- to 4-day prodrome of fever, malaise, headache, and backache before the development of the rash.
  E. The vesicles typically occur on an erythematous base (described as dewdrops on a rose petal)
  E. The vesicles typically occur on an erythematous base (described as dewdrops on a rose petal)

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  Explanation

  B. anthracis causes three diseases in humans: cutaneous, inhalation, and gastrointestinal anthrax. Cutaneous anthrax is the most common of the naturally occurring anthrax diseases. The spores of the gram-positive bacillus can survive for years in soil. The disease cutaneous anthrax occurs when the spores contaminate a wound on the skin of the victim and then start to grow. This disease occurs most commonly in agricultural areas where the soil becomes contaminated by the presence of animals. Initially

  a painless papule develops, followed by vesicles which then ulcerate and a black eschar forms. In the setting of cutaneous anthrax in a postal worker who has a coworker with an apparently similar disease, bioterrorism must be suspected. This type of attack occurred in the Fall of 2001, when anthrax spores were sent through the U.S. Postal system and over 20 persons were infected. In this setting, the most appropriate initial management is to immediately contact the appropriate Public Health Authorities,

  usually the local or state health department. Appropriate treatment will also need to be instituted, under the guidance of the public health specialists, as untreated cutaneous anthrax may carry a 20% mortality rate. Antibiotic therapy would usually be with ciprofloxacin, penicillin, or doxycycline. Anthrax does not spread from person to person, so quarantine is not necessary. Inhalation anthrax is caused by the direct inhalation of spores into the lungs and gastrointestinal anthrax, the least common of the anthrax

  syndromes, is caused by ingestion. Smallpox does not occur naturally anywhere in the world. Therefore, any suspicion of smallpox must be assumed to be a bioterror event and must be reported immediately to public health officials. Physicians should be able to recognize the signs and symptoms of smallpox and be able to distinguish them from the common occurrence of chickenpox. Chickenpox lesions tend to occur in clusters and evolve asynchronously. They are often described as "dew drops on a rose

  petal" as they are vesicles occurring on an erythematous base. The lesions tend to start on the trunk and rapidly spread outward. The rash will be associated with a fever but there are usually few to no prodromal symptoms. Because of the asynchronous growth and outbreaks, a patient will typically have lesions in different stages of evolution. In contrast, smallpox lesions tend to occur synchronously and the lesions tend to be uniform. The rash frequently occurs on the palms and soles. It typically starts on the

  face and arms and then spreads to the trunk and legs. The development of the rash tends to be slower than that of chickenpox. There is often a dramatic prodrome of high fever, malaise, headache, and backache for 24 days prior to the onset of the rash. Smallpox carries an approximately 30% mortality, while mortality associated with chickenpox is very low.

• Question 732:

  A19-year-old male who moved to your city 3 months ago comes to your office complaining of dry cough for the past 23 months. Along with the cough, he has had some shortness of breath with exertion. He denies fever, chills, nausea, vomiting, wheezing, and sneezing. The cough occurs mostly in the morning and improves as the day goes on. He denies similar complaints in the past and has no history of allergies. He says that his father had eczema and an allergy to eggs.

  The pulmonary function test that is most likely to be diagnostic in this patient is which of these?

  A. increased total lung capacity
  B. increased functional residual capacity
  C. increased residual volume
  D. decreased forced expiratory volume in 1 second (FEV1)
  E. decreased forced inspiratory volume
  D. decreased forced expiratory volume in 1 second (FEV1)

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  Explanation

  This patient is manifesting symptoms consistent with asthma. With the history of recently moving to a new area, along with a family history of allergies and eczema, his asthma may be further classified as allergic asthma. Episodic symptoms of cough, dyspnea, and wheezing are likely to occur. The diagnosis of asthma is made by demonstrating reversible airway obstruction. Airway obstruction is likely to be manifested by a reduction in the FEV1. An increase in the FEV1 of 15% after the use of a bronchodilator is the definition of reversibility. A CXR is most likely to be normal. Numerous cardiac conditions, such as CHF, cardiomyopathies, or pericardial effusions, may result in cardiomegaly on a CXR. Diffuse infiltrates may be seen with infections, interstitial lung disease, or other conditions. Flattened diaphragms would be consistent with prolonged obstructive lung disease, such as emphysema.

  The treatment of choice for the prevention of symptoms in all stages of asthma other than mild intermittent is inhaled steroid. All patients with asthma should also have a short-acting bronchodilator for acute symptomatic relief. A leukotriene modifier would be an alternative recommendation and might be a good addition to an inhaled steroid, as they also have FDA indications for patients with allergic rhinitis.

• Question 733:

  A 16-year-old girl is brought into the family practice clinic for her yearly health maintenance examination. Her height is average and her weight is above average. When this is mentioned to her, she blushes and quickly states that she is trying to lose weight. When asked further about her dieting habits, she eventually admits to routinely eating large amounts of food at one sitting, such as two pizzas, a large sandwich, and a gallon of ice cream. She also confides that she frequently will self-induce vomiting in order to compensate but denies laxative use. She realizes that her behavior is unhealthy, but she feels "out of control."

  Routine blood work would most likely demonstrate which of the following?

  A. acidosis
  B. hyperchloremia
  C. hypernatremia
  D. hypokalemia
  E. leucopenia
  D. hypokalemia

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  Explanation

  This patient is suffering from bulimia nervosa, categorized by recurrent episodes of binge eating associated with compensatory behaviors including self-induced emesis, diuretic, or laxative abuse. Because of the repeated vomiting of gastric fluids, patients are prone to develop various electrolyte abnormalities, such as hypochloremic alkalosis or hypokalemia. Hypernatremia and leukopenia are not commonly seen. Anticonvulsants, such as valproic acid and carbamazepine, as well as mood stabilizers such as lithium, may be helpful for treating comorbid bipolar disorder but are not in and of themselves efficacious in the treatment of bulimia nervosa. Similarly, antipsychotics and benzodiazepines may be used in co-occurring psychotic or anxiety disorders, but do not help with binging or purging. Antidepressants, especially the SSRIs, have been shown to be successful in decreasing both the binging and purging behaviors.

• Question 734:

  A21-year-old Asian female, with past medical history of exertional asthma, comes to your office complaining of mild low back pain. It started after her working out in the gym 3 days ago. The pain is 24 out of 10 in intensity, has no radiation, increases with bending or lying down for a long time, and improves with warm showers. You examine the patient, diagnose her with paravertebral muscle spasm, and give her prescriptions for cyclobenzaprine and naproxen to use as needed for pain and stiffness. You receive a call from your patient 2 hours later. She is having generalized itching, dizziness, and swelling of the tongue and lips. She is having difficulty breathing. She tells you that she took the first dose of the medication you prescribed about 30 minutes ago.

  What should you do at this time?

  A. Advise patient to use her albuterol inhaler as she is having an asthma attack.
  B. Advise her to take another dose of naproxen and stop cyclobenzaprine for now.
  C. Assure her that this is a common side effect to cyclobenzaprine; she will get used to it as she takes the next dose.
  D. Ask her to return to your clinic for evaluation.
  E. Ask her to call 911 immediately.
  E. Ask her to call 911 immediately.

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  Explanation

  This patient is exhibiting signs and symptoms of an anaphylactic reaction, likely to one of the medications that she recently took. Angioedema is occurring (swelling of the lips and tongue). Her dyspnea may be a manifestation of laryngeal edema or of bronchospasm. She is at high risk for respiratory compromise and, therefore, of the options listed, having her activate the emergency medical system is the most appropriate. Calling 911 from your office would be another option. Of the interventions listed, epinephrine would provide the most benefit in correcting the underlying problem. The alpha- and betaadrenergic effects result in vasoconstriction, bronchial smooth-muscle relaxation, and reduction on vascular permeability. Oxygen may be required if the patient is hypoxic, IV fluids may be necessary for persistent hypotension and albuterol may benefit the treatment of bronchospasm, but epinephrine would most immediately address the multiple systemic effects of anaphylaxis.

• Question 735:

  A 62-year-old man undergoes transplantation of a kidney from a cadaveric donor. The surgery is uncomplicated and his recovery proceeds well for the first week postoperatively. In the second postoperative week, he develops hypertension, peripheral edema, and decreased urinary output. He states that he has been taking his medications as ordered.

  What is the most likely cause of this condition?

  A. hyperacute organ rejection
  B. acute organ rejection
  C. chronic organ rejection
  D. congestive heart failure
  E. failure of physician to restart him on his preoperative furosemide
  B. acute organ rejection

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  Explanation

  In transplant immunology, a wide variety of immune effector mechanisms are responsible for rejection. Acute rejection typically occurs in the first few days to weeks after organ transplantation.The primary mediator of this immune response is the T cell. Treatment of acute rejection usually involves pulse dose steroids and increased immunosuppression. Other forms of rejection include hyperacute rejection and chronic rejection. Hyperacute rejection is the result of preformed antibodies and occurs within hours of transplantation and leads to graft loss. Chronic rejection occurs on the scale of months to years after transplantation and is characterized by fibrosis and loss of normal histologic architecture.

• Question 736:

  A 34-year-old female sex worker presents with a several week history of fatigue, malaise, fever, and a 10- lb weight loss. Over the last 2 weeks, the patient noted a rash on her face, torso, arms, legs, palms, and soles. The patient is HIV negative on a test 2 months ago, has had hepatitis B, gonorrhea, and chlamydia. The patient has an oral temperature of 100.6, and generalized lymphadenopathy. The patient does not have any lesions in the mucous membranes.

  

  What is the appropriate treatment?

  A. benzathine penicillin 2.4 million units IM weekly for 3 weeks
  B. azythromycin 1 g orally
  C. aqueous penicillin 4 million units intravenously every 4 hours for 14 days
  D. doxycycline 100 mg twice a day for 2 weeks
  E. oral corticosteroids over 5 days
  A. benzathine penicillin 2.4 million units IM weekly for 3 weeks

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  Explanation

  The skin lesions as shown in Figures show erythematous maculopapular lesions. There are only a few conditions that cause a rash on the palms and soles. These include syphilis, gonorrhea, and Stevens- Johnson syndrome. Disseminated gonnorhea does not cause lesions on the face. This is not a potential presentation of hepatitis B or chlamydia. Askin biopsy is not indicated. RPR and MHA-TP tests will be positive in syphilis in a high titer. All patients with syphilis need to have HIV testing. The rash of primary HIV infection is a faint erythematous rash on the trunk and is not always present. Early in primary HIV infection, a PCR determination can be negative. In the absence of neurosyphilis, benzthine penicillin 2.4 million units IM weekly for 3 weeks is the treatment of choice for patients with syphilis of unknown duration or greater than a year. While azithromycin 1 g orally will treat gonorrhea and chlamydia, it will not treat syphilis. Aqueous penicillin 4 million units intravenously every 4 hours for 14 days is the treatment of choice for neurosyphilis. An alternate treatment for latent syphilis in patients who are penicillin allergic is doxycycline 100 mg twice daily for 30 days. Oral corticosteroids are not indicated in this case.

• Question 737:

  A 54-year-old man presents with a 3-cm right thyroid nodule that was found incidentally by the patient while shaving. He denies any pain or discomfort. He denies any history of thyroid disease, any family history of thyroid disease, and any history of head/neck irradiation. He notes a 10-lb weight loss over the past 6 months. His examination is only remarkable for the firm right thyroid nodule. The remainder of the thyroid is not palpable. There is no adenopathy. Heart rate is 90/minute and regular. The skin is warm and moist, and a fine tremor is present when he holds his hands out. TSH level is <.02 U/mL.

  Which of the following is the most appropriate next step?

  A. thyroid ultrasound
  B. antithyroid peroxidase antibodies
  C. thyroid-stimulating immunoglobulins
  D. fine needle aspiration of the nodule
  E. thyroid nuclear scan
  E. thyroid nuclear scan

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  Explanation

  The very low TSH suggests that the patient is hyperthyroid, most likely because of an autonomously functioning thyroid adenoma or hot nodule. In general, these nodules are more than 3 cm in diameter in order to be associated with hyperthyroidism. They are associated with a very low rate of malignancy and do not require fine needle aspiration. The diagnosis would be confirmed by the finding of uptake in the area of the nodule on scan with suppression of uptake in the rest of the thyroid.

• Question 738:

  A 55-year-old woman presents to your office with painful hands, causing difficulty opening jars and turning the key in the ignition of her car. She is fatigued and she notices joint stiffness, but limbers up by lunch. She has trouble getting her rings off because of enlarging knuckles. About a year ago, she tried some OTC ibuprofen, which seemed to help, but led to the development of a bleeding ulcer severe enough to require transfusion and ICU care. Otherwise, her health is good, and her review of systems is negative. Your physical examination reveals tenderness and swelling at the index proximal interphalangeal and metacarpophalangeal joints bilaterally. There are small effusions on both knees. She has tenderness to lateral compression of the forefoot area bilaterally.

  The test ordered above is negative and an anticyclic citrullinated peptide (anti-CCP) antibody is strongly positive (600). Which of the following is the probable source of her symptoms?

  A. cryoglobulinemia
  B. osteoarthritis
  C. polymyalgia rheumatica
  D. SLE
  E. RA
  E. RA

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  Explanation

  In all likelihood, this patient is presenting with a systemic inflammatory arthritis. Clearly, treatment will need to be initiated. In order to effectively and promptly treat her, you will need to understand the current state of her physiology. Therefore, basic laboratory studies including blood count, full chemistries, and urinalysis should be obtained. At this point, the most likely diagnosis is RA, and the rheumatoid factor and sedimentation rate may be helpful. Theoretically, sarcoidosis can present in this way but, epidemiologically, this is much less likely. Because of this and because the ACE level is fairly nonspecific, it should not be part of the initial workup. Neither joint fluid aspiration nor uric acid levels are likely to be diagnostic. The elevation of serum transaminase in the face of elevated sedimentation rate, moderate or low positive ANA, and rheumatoid factors raise the question about hepatitis C.

  About 50% of patients with active hepatitis C will have cryoglobulinemia. Cryoglobulins can produce low moderate positive rheumatoid factors. Therefore, it is extremely important in this circumstance to be certain that hepatitis C is not present. With such a low positive ANA, the likelihood that this is classical Lupus is low, and double-stranded DNA antibodies are not likely to be revealing. C-reactive protein may confirm the presence of inflammation, but it won't provide additional information over the sedimentation rate. Syphilis, "the great imitator," again may occasionally have arthritis as a manifestation--but rarely without other features. The remaining studies while they might be useful later but are unlikely to be helpful as the next most important test obtained. The probable source of the patient's symptoms is RA. Osteoarthritis can produce articular swelling, but on physical examination, there is rarely bogginess in the synovium. Anti- CCP antibody is an antibody directed against the citrullinated portion of fillagen. It has the highest specificity for RA of any antibody known. It is usually present early and may predict more severe disease.

• Question 739:

  You see a 2-month-old infant in the emergency department for vomiting. The mother says that the baby has been spitting up more over the past few days and has become more irritable. She denies any fever, diarrhea, or change in formula. The mother tells you that there is a family history of "heartburn" and that her other children have all spit up. The infant has some emesis in the emergency department that seems to be formula mixed with some bile. The infant is intermittently irritable and sleepy.

  What is the most concerning diagnosis that this could be?

  A. biliary atresia
  B. malrotation
  C. pyloric stenosis
  D. imperforate anus
  E. diaphragmatic hernia
  B. malrotation

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  Explanation

  Bilious emesis in an infant is malrotation until proven otherwise. Malrotation can lead to a midgut volvulus. The volvulus can result in bowel ischemia and necrosis. This makes bilious emesis in a newborn a concerning finding. Pyloric stenosis would cause nonbilious emesis. Imperforate anus would present with the failure of stool passage. Diaphragmatic hernia will present with poor feeding, drooling, and respiratory embarrassment The best radiographic test in the diagnosis of malrotation is an UGI contrast study with small bowel follow through. This will identify the duodenum and its location relative to the ligament of Treitz. The characteristic finding in a midgut volvulus is the "corkscrew" sign, which is seen as contrast media traverses the kinked intestine. An abdominal CT may show malrotation but is less specific for it. Barium enema and radionuclide scans have no role in the diagnosis of malrotation.

• Question 740:

  Apatient with a known family history of multiple endocrine neoplasia (MEN) I, now presents with intractable ulcer disease.

  Which of the following statements about his condition is most accurate?

  A. Diarrhea is a frequent complaint.
  B. Tumors are rarely multiple.
  C. Tumors are rarely malignant.
  D. An elevated fasting gastrin level is diagnostic for the Zollinger-Ellison syndrome.
  E. CT is useful in localizing the tumor in greater than 75% of patients.
  A. Diarrhea is a frequent complaint.

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  Explanation

  The Zollinger-Ellison syndrome was described in 1955, in two patients with the triad of gastroduodenal ulcerations, gastric hypersecretion, and nonbeta islet cell tumors of the pancreas. Gastrinomas arise from neuroendocrine cells and represent the third most common neuroendocrine tumors (after carcinoids and insulinomas). These tumors are associated with MEN I. These tumors occur predominantly in the pancreas, duodenum, antrum, and peripancreatic lymph nodes, but can also occur at distant sites like the ovary. Isolated tumors are found in 50%, and multiple tumors in 50%, but there is a higher incidence of multiple tumors in MEN I. Tumors are malignant in 50%, with metastases to the regional lymph nodes and the liver. Once the diagnosis has been established, tumor localization can be achieved with indium-labeled octreotide scan, CT with fine cuts through the pancreas, ultrasound, MRI, or selective angiography. None of these tests are highly sensitive, and often the tumors are not localized until the time of exploration and intraoperative-directed ultrasonography.