USMLE USMLE Certifications USMLE Questions & Answers

• Question 451:

  A 19-year-old female is brought to the emergency department after she collapsed while jogging. She has a history of anorexia nervosa. When she regains consciousness, she says as she was jogging she became lightheaded, broke out into a sweat, and had palpitations. Her fingerstick glucose is 40 mg/dL. Her palpitations and diaphoresis were most likely caused by

  A. ACTH

  B. calcitonin

  C. epinephrine

  D. insulin

  E. thyroxine

  Correct Answer: C

  Explanation:

  Exercising in patients with anorexia nervosa can trigger or worsen the effects of hypoglycemia. This occurs because lipid stores are not available to meet the current energy needs. The body responds to the hypoglycemia with an epinephrine burst from the adrenal medulla. The lack of available glucose and ATP for the brain causes dizziness or lightheadedness. Sympathetic activation by epinephrine leads to the induction of gluconeogenesis, stimulation of cardiac beta-1 receptors and stimulation of skin receptors.

• Question 452:

  A 40-year-old male comes to his physician due to progressive muscle weakness and paralysis. Over the next few years, his condition progresses to complete paralysis of all voluntary muscles and he eventually dies of respiratory failure. Microscopic examination of tissue obtained at autopsy shows that both upper and lower motor neurons are degenerated. Of the listed options, the location which would likely reveal the most marked neuronal loss is the

  A. caudate nucleus

  B. cerebellum

  C. globus pallidus

  D. spinal cord

  E. substantia nigra

  Correct Answer: D

  Explanation:

  Amyotrophic lateral sclerosis (ALS) commonly known as Lou Gehrig disease is a devastating disease characterized by the degeneration of both upper and lower motor neurons. Depending on the stage of the disease, patients may primarily experience either upper motor symptoms (hyperreflexia, spasticity, Babinski reflex) or lower motor symptoms (weakness, muscular atrophy, fasciculations) usually both. Upper motor neurons are located in the motor area of the cerebral cortex and lower motor neurons are located in the anterior horn of the spinal cord. ALS may be caused be a defect in superoxidase dismutase

  1. There is no effective therapy although riluzole may be used to manage symptoms.

• Question 453:

  A 1-week-old male is brought to the emergency department by his mother due to persistent crying and bloody diarrhea. She says he was delivered at 33 weeks’ gestation and has been bottle-fed since then.

  Physical examination reveals a rigid abdomen. The neonate undergoes emergency surgery to resect a portion of his small intestine during which bowel perforation is confirmed. Microscopic examination of the excised bowel will most likely reveal:

  A. inflammatory polyps

  B. multiple diverticula

  C. neoplastic polyps

  D. thickened collagenous bands

  E. transmural necrosis

  Correct Answer: E

  Explanation:

  Necrotizing enterocolitis is usually seen in premature, formula-fed infants. Typically, the infants presents with severe abdominal distress in the first week of life. Intestinal is chemia and poor neonatal immune response contribute to the condition and both the small and large bowel may be affected. Necrotizing enterocolitis may be complicated by necrosis of the intestinal mucosa with possible perforation which can lead to pneumatosis intestinalis seen on an abdominal X-ray.

• Question 454:

  A 50-year-old male comes to the physician complaining of neck masses that have been increasing in size for the past six months. He denies having any fevers or night sweats. Physical examination reveals bilateral, nontender cervical lymphadenopathy and hepatosplenomegaly. Biopsy of a cervical node reveals architectural distortion of the lymph node with proliferation of enlarged germinal follicles. Flow cytometry reveals a predominant cell population of CD10+, CD19+ and CD20+ cells. The most likely cause of these findings is

  A. bcl-2 activation

  B. bcl-16 activation

  C. c-myc activation

  D. t(8;14)

  E. t(9;22)

  Correct Answer: A

  Explanation:

  Diffuse large B-cell lymphoma is derived from the B-cell line and the neoplastic cells resemble germinal center B cells. It may result from a follicular lymphoma. It is the most common type of non-Hodgkin lymphoma in adults but can occur in children. It results from alterations to the bcl-2 and bcl-6 proteins. The bcl-2 protein inhibits apoptosis, leading to prolonged cell survival. Patients may present with constitutional symptoms (low grade fever, weight loss, night sweats), nontender lymphadenopathy and the spleen, liver and bone marrow may be involved. The prognosis for diffuse large B-cell lymphoma is poor.

• Question 455:

  A 35-year-old male comes to the physician due to fatigue. He recently returned from a trip to Japan. Laboratory results are as follows:

  Hemoglobin – 9 g/dL Mean corpuscular volume – 108 fl MCHC – 33 g/dL Mean corpuscular hemoglobin – 35 pg

  A peripheral blood smear is obtained which reveals enlarged red blood cells and hypersegmented neutrophils. These findings were most likely caused by

  A. Diphyllobothrium latum

  B. Echinococcus granulosus

  C. Onchocerca volvulus

  D. Schistosoma haematobium

  E. Taenia solium

  Correct Answer: A

  Explanation:

  Diphyllobothrium latum is a tapeworm which can cause vitamin B12 deficiency because it competes for this vitamin in the small intestine. Infection with this tapeworm occurs after consumption of raw or undercooked fresh water fish. Vitamin B12 deficiency may occur in infected patients and presents with fatigue due to the macrocytic megaloblastic anemia with hypersegmented neutrophils. Treatment of the infection is with praziquantel.

• Question 456:

  A 35-year-old male comes to the physician due to fatigue. He recently returned from a trip to Japan. Laboratory results are as follows:

  Hemoglobin – 9 g/dL Mean corpuscular volume – 108 fl MCHC – 33 g/dL Mean corpuscular hemoglobin – 35 pg.

  A peripheral blood smear is obtained which reveals enlarged red blood cells and hypersegmented neutrophils. The most appropriate pharmacologic treatment for this patient is with

  A. albendazole

  B. diethylcarbamazine

  C. ivermectin

  D. metronidazole

  E. praziquantel

  Correct Answer: E

  Explanation:

  Diphyllobothrium latum is a tapeworm which can cause vitamin B12 deficiency because it competes for this vitamin in the small intestine. Infection with this tapeworm occurs after consumption of raw or undercooked freshwater fish. Treatment of infection with Diphyllobothrium latum is with praziquantel. Praziquantel is an antihelminth medication which works by increasing the cell membrane permeability to calcium and causing paralysis of the worms. It is also used to treat infection with Taenia solium, Echinococcus granulosus, Schistosoma haematobium and Clonorchis sinensis.

• Question 457:

  A 30-year-old prim gravid female at 16 weeks' gestation comes to the physician for a routine prenatal examination. She has no pre-existing medical conditions and thus far her pregnancy has been uncomplicated. She currently takes prenatal vitamins and iron supplements. Vitals reveal a blood pressure of 160/110 mmHg. Urinalysis reveals 3+ proteinuria. The most likely cause of these findings is

  A. anencephaly

  B. hydatidiform mole

  C. maternal renal disease

  D. neural tube defects

  E. twin gestation

  Correct Answer: B

  Explanation:

  Although this patient has high blood pressure and proteinuria, one of the major diagnostic criteria for preeclampsia is onset of symptoms after 20 weeks of gestation. Development of these symptoms before the 20th week of pregnancy is suggestive of the presence of a hydatidiform mole which is a form of gestational trophoblastic disease characterized by “early pre-eclampsia,” uterine enlargement, vaginal bleeding, passage of soft, edematous, grapelike tissue and significantly elevated beta-human chorionic gonadotropin (beta-hCG). Hydatidiform moles may be either complete moles or partial moles. The diagnosis may be made by ultrasound, but definitive diagnosis is confirmed by histopathologic examination. Treatment is with methotrexate, dilation and curettage.

• Question 458:

  A 2-week-old male is brought to the physician by his mother due to labored breathing for the past day. She had a home delivery which she reports as uneventful but say she developed "pink-eye" after the first week. Vitals reveal a respiratory rate of 40/min. Physical examination reveals bilateral inspiratory crackles and faint wheezing in both lungs. Laboratory studies reveal a leukocyte count of 15,000/mm³ with 10%

  A. Ascaris lumbricoides

  B. Chlamydia trachomatis

  C. Haemophilus influenza

  D. Mycoplasma pneumoniae

  E. Neisseria gonorrhea

  Correct Answer: B

  Explanation:

  This neonate's clinical findings are consistent with neonatal atypical pneumonia secondary to Chlamydia trachomatis types D–K. Transmission occurs from the mother's vaginal canal to the neonate at birth. A classic presentation includes neonatal conjunctivitis 1-2 weeks after birth, clinical signs of pneumonia, eosinophilia and a staccato cough. A chest x-ray may show scattered infiltrates and hyperinflation of the lungs. Neonatal conjunctivitis can occur if prophylactic erythromycin eye drops are not given immediately after delivery. Gonococcal conjunctivitis typically occurs 2-7 days after birth, while chlamydial conjunctivitis has a later onset than gonococcal conjunctivitis with an incubation period of 5-14 days.

• Question 459:

  A 45-year-old male who has a BMI of 42 kg/m² undergoes a myocardial perfusion scintigraphy due to frequent chest pain during strenuous activities. An angiogram had earlier revealed a 95% occlusion in the proximal segment of his left circumflex coronary artery. There were no changes in the other coronary arteries. The most likely other finding in this patient is

  A. inducible myocardial ischemia in the anterior segment of the left ventricle

  B. inducible myocardial ischemia in the anteroseptal segments of the left ventricle

  C. inducible myocardial ischemia in the inferior segments of the right ventricle

  D. inducible myocardial ischemia in the inferolateral segment of the left ventricle

  E. inducible myocardial ischemia in the septal segments of the left ventricle

  Correct Answer: D

  Explanation:

  The left circumflex coronary artery supplies the lateral (or posterolateral) and posterior walls of the left ventricle as well as the anterolateral papillary muscles of the left ventricle. An occlusion of this coronary artery will cause diminished blood flow in these areas and inducible ischemia.

• Question 460:

  A 45-year-old female comes to the physician with joint pain, swelling and morning stiffness which improves with use. She also reports weight loss of 3 kg (6.6 lbs). Laboratory tests reveal the presence of serum rheumatoid factor. Before prescribing etanercept, the physician should obtain a:

  A. complete blood count

  B. electrocardiogram

  C. liver function test

  D. purified protein derivative test

  E. thyroid function test

  Correct Answer: D

  Explanation:

  This patient most likely has rheumatoid arthritis (RA) which is an autoimmune disease characterized by inflammation and erosion of articular cartilage and bone. It presents with weight loss, fatigue, joint pain, swelling and morning stiffness which lasts longer than an hour and improves with use. It usually involves the metacarpophalangeal joints, proximal interphalangeal joints and the wrist joints. Joint findings include soft tissue swelling, joint space narrowing and subchondral cysts. Management of RA includes treatment with NSAIDs, glucocorticoids, methotrexate, hydroxychloroquine and biologic agents like TNF-alpha inhibitors such as etanercept. Etanercept is a fusion protein which comprises of a decoy receptor for TNF-alpha and the Fc portion of IgG. It is produced by recombinant DNA and approved for use in rheumatoid arthritis, psoriasis and ankylosing spondylitis. TNF-alpha inhibitors predispose patients to developing tuberculosis due to the reactivation of latent TB hence a purified protein derivative (PPD) test is required before etanercept is prescribed.