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

USMLE USMLE-STEP-3 Online Questions & Answers

• Question 101:

  A mildly mentally retarded 9-year-old girl is brought to your office for acne. On examination, she does not actually have acne but has small flesh colored papules along her nasolabial fold. Her past history is significant for having had a first (afebrile) seizure last year. The mother reminds you that she has a faint birthmark on her hip that is pale and becomes more prominent in the summer, when the child's skin tans. Examination of this area reveals a 5-cm oval patch that is hypopigmented. Which condition would she most likely have?

  In evaluating her first seizure, a head CT was performed. Which finding would be most consistent with her diagnosis?

  A. frontal cortical atrophy with dysplastic vessels
  B. periventricular "tubers"
  C. diffuse white matter calcifications
  D. hydrocephalus from aqueductal stenosis
  E. poor gray-white differentiation
  B. periventricular "tubers"

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  Explanation

  Children with tuberous sclerosis (tuberous sclerosis complex, TSC) can develop nasolabial fold angiofibromas (commonly referred to adenoma sebaceum). These can be mistaken for acne in an adolescent and is seen in over 80% of adolescents with TSC. Other cutaneous findings include peri- and subungual fibromas, ash leaf spots (hypomelanocytic macules), and shagreen patches. Skin findings are seen in 75% of cases of tuberous sclerosis. Tuberous sclerosis can also have CNS cortical defects and "tubers," which may be foci of seizure activity. The "tubers" have a classic periventricular distribution. Mental retardation is very common in varying degrees. Sturge-Weber syndrome (also known as leptomeningeal angiomatosis) is a port wine stain, typically with V1 or V2 distribution, with an underlying leptomeningeal blood vessel dysplasia. These dysplastic vessels will typically result in an underlying cortical atrophy. This cortical atrophy can be a nidus for seizures and can be seen on a CT scan of the head. Neurofibromatosis, type 1 is polymorphous neurocutaneous syndrome. The most common findings are caf?au lait spots, which may be present at birth and worsen during puberty. Beckwith-Wiedemann syndrome and CHARGE association are discussed further in explanations 44 and 45

• Question 102:

  Deficiency of which of the following is the most common nutritional cause of anemia?

  A. calcium
  B. vitamin B12 deficiency
  C. iodine
  D. iron
  E. vitamin C
  D. iron

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  Explanation

  Iron deficiency is a common finding. Most proprietary infant formulas have iron supplementation. Infants who are strictly breast fed may require oral iron supplementation. A total body iron deficiency can result in a microcytic, hypochromic anemia. Testing of total serum iron, ferritin, and total iron binding capacity can help clarify the body iron stores.

• Question 103:

  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.

  Which of the following would be the most appropriate initial test?

  A. abdominal computed tomography (CT)
  B. barium enema
  C. abdominal ultrasound
  D. UGI series with small bowel follow through
  E. radionuclide scan
  D. UGI series with small bowel follow through

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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 104:

  A 65-year-old White woman presents to your office and requests to have a screening test for osteoporosis. She has been menopausal for 15 years. She never took hormone replacement therapy (HRT). She currently takes 500 mg of calcium a day and walks 2 miles a day. She has no history of fractures.

  The result of the test that you ordered shows the patient's bone mineral density to be 2.5 standard deviations below the mean bone density of a 25-year-old woman. What is the most appropriate management at this point?

  A. start therapy with an oral bisphosphonate
  B. increase her calcium supplement to 1000 mg/day
  C. suggest diet and exercise changes then recheck her bone density in 6 months
  D. add vitamin D and continue her current calcium supplement
  E. no intervention as her bone density is considered normal for her age
  A. start therapy with an oral bisphosphonate

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  Explanation

  Explanations:

  DEXA is the most widely used test for the screening and diagnosis of osteoporosis. It is sensitive for the loss of bone density, exposes the patient to a relatively low dose of radiation, and is widely available at a reasonable cost. It is the mode of evaluation that has been used in most of the studies of the evaluation and management of osteoporosis. The American College of Radiology Guidelines state that DEXA of the lumbar spine and proximal femur is the most appropriate screening test for osteoporosis in postmenopausal women who are not on any therapy. Quantitative CT scanning is also highly sensitive but is less widely available, more expensive, and exposes the subject to higher radiation doses. Lateral thoracic spine radiographs can diagnose or confirm the presence of osteoporotic fractures but are not appropriate as a screening test for bone density. Quantitative ultrasonography, usually of the calcaneus or digits, is becoming more widely available at low costs, but has the disadvantage of being unable to directly evaluate the areas where most ostoporotic fractures are likely to occur-- hip, spine, and radius. SXA has not correlated as well to fracture risk as dual energy techniques and is, therefore, less appropriate than DEXA.

• Question 105:

  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. The patient's symptoms do not respond to your initial therapeutic management. You suspect that his condition is refractory to treatment. Which of the following should you consider at this time?

  A. He may have human immunodeficiency virus (HIV) infection and should be tested.
  B. His condition will require high doses of prednisone (60 mg daily) for adequate control.
  C. His joints are obviously not infected and should be directly injected with corticosteroids.
  D. He must have a disseminated bacterial infection that will require IV antibiotics.
  E. He is resistant to indomethacin, so the dose should be doubled to 400 mg daily.
  A. He may have human immunodeficiency virus (HIV) infection and should be tested.

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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 106:

  A 72-year-old man comes to your clinic for the first time, accompanied by his wife. His wife states that she is concerned because he has been growing increasingly forgetful over the past year. Within the past month, he has forgotten to turn off the stove and has got lost while walking to the post office one block away from their home. His past medical history is significant for well-controlled diabetes and chronic lower back pain. He has no history of falls or traumatic injury to the head. Examination of the patient is significant for a score of 18 on a Mini Mental Status Examination (MMSE). During the administration of the MMSE, the patient blurts out that his wife brought him to the doctor because she is having an extramarital relationship. Despite appropriate treatment, the patient experiences a gradual decline in mental function. He develops erratic sleep habits, frequently awakening at night and wandering throughout his home. His wife states that she once found him sitting on the ground in their yard, unable to recall how he arrived there. During your latest examination of the patient, you note that he has lost the ability to sign his name, holding the pen as if he is unsure of what to do with it. Exasperated, his wife states that he is now dependent on her for performance of his activities of daily living. Which of the following is indicated in the treatment of the patient's condition at its current severity?

  A. tacrine (Cognex)
  B. gingko biloba
  C. rivastigmine (Exelon)
  D. memantine (Namenda)
  E. galantamine (Reminyl)
  D. memantine (Namenda)

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  Explanation

  This patient's symptoms are most consistent with Alzheimer disease. Alzheimer disease is a prominent condition in developed nations, ranking as the third most common terminal illness behind heart disease and cancer. It is the most common form of dementia, with over 4 million Americans having the condition in the United States alone. There is a direct correlation between advanced age and increasing prevalence of Alzheimer disease. While there is an early-onset form of familial Alzheimer disease that may appear as early as the third decade of life, this accounts for only a small percentage of total Alzheimer cases. There does appear to be a genetic component to the development of Alzheimer disease, as it has been demonstrated that first-degree relatives of Alzheimer patients possess an increased risk for development of the condition. Genes on chromosomes 1, 14, and 21 have been implicated in this association. While age and family history are important risk factors, there is no evidence proving that environmental factors lead to an increased chance for development of the disease. Progression of Alzheimer dementia is typically insidious, spanning as many as several years.

  Anticholinergic agents and any other medication with anticholinergic effects are contraindicated in the setting of Alzheimer dementia. Their use may lead to worsening of cognition and may contribute to decreased efficacy of medications used in the treatment of Alzheimer dementia. Tricyclic antidepressants such as amitriptyline should be avoided for this reason. Risperidone, olanzapine, and quetiapine are atypical antipsychotic medications which are useful in the treatment of emotional withdrawal and delusions which may arise in Alzheimer patients. Trazodone, carbamazepine, and divalproex are moodstabilizing medications which are useful in patients who display marked agitation. While trazodone does display some anticholinergic side effects, they are far less pronounced than those seen with amitriptyline.

• Question 107:

  You see a 31/2-year-old child in the emergency department who has had fever for the past week. The parents relate that their son has some swollen glands, fever, and now seems to be getting a rash on his arms. On examination, you find an uncomfortable appearing young boy whose vital signs are normal with the exception of a temperature of 104. You note t hat he has a red posterior oropharynx with dry, cracked lips. His TMs are normal. He has mild conjunctival injection bilaterally without any discharge.

  His chest is clear, and his heart sounds are normal. He does not have any hepatosplenomegaly. His has a lacy, confluent macular rash on his chest and upper arms, with mild peeling of the tips of his fingers.

  What is the most worrisome complication of this disease?

  A. encephalitis
  B. coronary artery aneurysm
  C. cardiac valve dysfunction
  D. intracerebral hemorrhage
  E. hemorrhagic stroke
  B. coronary artery aneurysm

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  Explanation

  Kawasaki disease (mucocutaneous lymph node syndrome) is a disease of unclear etiology. The salient diagnostic features include fever for greater than 5 days, cervical lymph node greater than 1 cm, nonpurulent conjunctivitis, oral changes (cracking lips or "strawberry tongue"), polymorphous rash to the trunk, and changes to the hands and feet (peeling of the fingers or toes or edema of the hands or feet). This may be confused with group Abeta-hemolytic streptococcal pharyngitis, which usually is not associated with conjunctivitis. Coxsackie viral infection is commonly seen as the "hand-footmouth" disease, with shallow ulcers on the palms, soles, and in the mouth. There is nominal fever associated, and conjunctivitis is uncommon. Parvovirus B-19 (erythema infectiosum, "fifth disease") is commonly called "slapped cheek" disease because of the exanthem of bright red cheeks. Adenopathy and conjunctivitis are not features of this infection. Acute phase reactions are often elevated late in the course of Kawasaki disease.

  The most common blood test result would be a dramatically elevated platelet count. It is usually greater than 750,000 and can be greater than 1,000,000. An ESR is also likely to be elevated, not low. Apositive rapid strep test would lead one more toward acute GAS disease. The treatment of choice for Kawasaki disease is IVIG and aspirin. IVIG infusion is usually over 12 hours and will commonly result in rapid defervescence and clinical improvement. Treatment of Kawasaki disease is important as it will prevent long-term sequelae. A common side effect of IVIG is aseptic meningitis. Nearly a quarter of untreated children will develop coronary artery dilatation. This is most common cause of acquired heart disease in children younger than 5 years of age. The coronary artery dilatation can result in aneurysm formation and myocardial infarction.

• Question 108:

  A20-year-old male has had a recent wide local excision of a 1.5 mm melanoma from the right ankle. There is no evidence of metastatic disease. The most important prognostic factor for this patient is which of the following?

  A. the Breslow depth of the tumor
  B. the Clark level of the tumor
  C. the location of the tumor
  D. the age of the patient
  E. the number of prior severe blistering sunburns
  A. the Breslow depth of the tumor

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  Explanation

  In patients who have melanoma that is confined to the skin (i.e., no evidence of metastatic disease), the most important prognostic factor is the Breslow histologic depth of the tumor. The age of the patient and location of the tumor also play a role in prognosis, but to a lesser degree. The forearm and leg tend to have a better prognosis; scalp, hands, feet, and mucous membranes have a worse prognosis. Older persons tend to have poorer prognoses, as well. Standard treatment for melanoma involves surgical excision. Sentinel lymph node biopsy should also be performed in any patient who has a melanoma that is at least 1 mm thick. This aids in determining whether melanoma cells have metastasized to the local lymph node basin. If the sentinel lymph node biopsy is negative for melanoma cells, no further lymph node studies are necessary. However, a positive biopsy warrants complete lymph node dissection. In addition to this situation, complete lymph node dissection is indicated in the setting of clinical lymphadenopathy regardless of evident distant metastasis. High dose interferon alpha-2 therapy is aviable option for use as adjuvant therapy in patients at high risk for disease recurrence, having been shown to prolong periods of remission and possibly improve mortality. Single-agent chemotherapy is generally used in patients with stage IV melanoma and is considered more for palliative purposes.

• Question 109:

  A4-year-old boy is brought into the emergency room by his mother for evaluation. When the child is asked regarding specific complaints, he looks anxiously away and states, "It hurts when I go pee-pee." His mother confidently adds, "He has another urinary tract infection (UTI)." She lists the antibiotics that he has been treated with in the past and then demands that he be admitted for a workup. On examination, his vitals signs are unremarkable except for a temperature of 102. His physical examination is notable for suprapubic tenderness and some evidence of recent urethral trauma. His urinalysis is consistent with a UTI. Further review of his medical chart reveals multiple emergency room visits for various physical complaints including similar presentations for recurrent UTIs. Prior inpatient and outpatient assessments have not been able to adequately account for any underlying etiologies.

  What is the most likely explanation for the mother's behavior?

  A. conscious production of symptoms to assume the sick role
  B. conscious production of symptoms to obtain secondary gain
  C. expectable reaction from a concerned parent
  D. hysterical reaction from an overly concerned parent
  E. unconscious production of symptoms due to unconscious conflict
  A. conscious production of symptoms to assume the sick role

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  Explanation

  The child's mother demonstrates factitious disorder by proxy, categorized by a parent or caretaker intentionally inducing an illness in someone under their care. Confronting the mother in the emergency room setting would likely lead to defensiveness, denial, and anger. The mother could possibly leave abruptly with the child. Having a psychiatrist present in this situation may also create a similar result. While a referral to urology and treatment of the infection may be indicated and appropriate, it does not address the immediate concern, which is the mother's abuse of her son. As factitious disorder by proxy is considered a form of child abuse, the physician has the legal obligation to notify child protective services. Admitting the boy to the hospital will both enable treatment of his medical illness and provide time for the proper authorities to intervene if necessary. The conscious production of symptoms for secondary gain (e.g., avoidance of work, school, jail, military service) is the rationale behind malingering.

  Although the mother's apparent concern for her child may appear expectable, her elaborate methods of abusing her son demonstrate significant pathology. The unconscious production of symptoms or signs due to unconscious conflict is the classic drive in conversion disorder. The motivation for factitious disorder is believed to be the purposeful production of an illness in order to assume the sick role (DSM IV-TR).

• Question 110:

  The modern history of the protection of human research subjects began in the twentieth century in response to human experimentation which occurred during World War II. The Nuremberg Military Tribunal set forth initial basic standards for the conduct of research which ultimately became known as the Nuremberg Code (1947/1948). In subsequent years, these recommendations have been modified and expanded to reflect various aspects of medical ethics in biomedical and behavioral research. These international ethical guidelines include the Declaration of Helsinki (1964), the Belmont Report (1979), CIOMS (1982), and the Common Rule (1991).

  The concept of justice as described in the Belmont Report means which of the following?

  A. ensuring that risks to research subjects are minimized
  B. ensuring the protection of privacy
  C. maintaining confidentiality
  D. ensuring informed consent
  E. ensuring the equitable distribution of research burdens and benefits
  E. ensuring the equitable distribution of research burdens and benefits

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  Explanation

  On September 30, 1978, the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research submitted the report "Ethical Principles and Guidelines for the Protection of Human Subjects of Research," named after the Belmont Conference Center in the Smithsonian Institution. The three ethical principles emphasized in this report include justice, beneficence, and respect for persons. Justice is the equitable distribution of research burdens and benefits. Beneficence is the mechanism to maximize benefits and minimize harm to research subjects. Respect for persons is the ethical principle which prioritizes the respect for individual autonomy and the protection of individuals with reduced autonomy. The principle of respect emphasizes the protection of subjects' privacy, maintenance of confidentiality, informed consent, and the utilization of additional safeguards for the protection of vulnerable populations. Health and Human Service (HHS) regulations delineate additional mechanisms to protect human subjects, which include (1) institutional assurances of compliance, (2) Institutional Review Board (IRB) review, and (3) informed consent. An institutional assurance of compliance is documentation that the institution will follow HHS regulations for the protection of human subjects. An IRB is a committee that has been established to protect human subjects involved in research activities. These committees must have at least five members of varying backgrounds who possess the professional competence to review research activities.

  Informed consent is the voluntary choice of an individual to participate in research activities. To be truly informed consent, the individual must have a clear and accurate understanding of the purpose of the research, the risks involved, the potential benefits, the procedures to be performed and the alternative modalities of treatment available. Typically, these are in a written consent form. The legal arguments for informed consent emphasize the right of self determination. This is in contrast to the ethical basis of individual autonomy. Therefore, a mere signature by the individual participant does not fulfill the ethical requirements of the informed consent process. Any research study must have scientific validity, a fair selection of individual subjects for populations, protection of vulnerable populations, fair access to the benefits of medical research, acceptable risk- benefit ratios, appropriate informed consent, and independent review of the study. In addition, Data Safety Monitoring Boards are being utilized to further monitor the safety of research protocols and participation.