USMLE USMLE Certifications USMLE-STEP-1 Questions & Answers

• Question 221:

  A 3-day-old male infant is diagnosed with meconium ileus. You should be concerned that he has which of the following conditions?

  A. alkaptonuria

  B. cystic fibrosis

  C. hemophilia A

  D. phenylketonuria

  E. Wilson disease

  Correct Answer: B

  Section: Pathology and Path physiology Meconium ileus is a very common early clinical expression of cystic fibrosis. Increased sweat sodium chloride level confirms the diagnosis. About 70% of children with cystic fibrosis have a deletional abnormality of chromosome 7. Pancreatic insufficiency, recurrent pulmonary infections, and biliary obstruction may complicate the disorder. Alkaptonuria (choice A) is an autosomal recessive disease that causes abnormal pigmentation and degeneration of cartilage. Hemophilia A(choice C) is an X- linked hereditary disease caused by a relative lack of coagulation factors VIII or IX. Phenylketonuria (choice D) is due to a hereditary lack of the enzyme phenylalanine hydroxylase. Mental retardation is the major clinical finding. Wilson disease (choice E) is an autosomal recessive disorder of copper accumulation that principally affects the liver and brain.

• Question 222:

  A 46-year-old woman with a 30-year history of juvenile diabetes undergoes a left renal allograft for advanced diabetic nephropathy. The transplant is initially successful; however, 3 months later she develops an unproductive cough with associated arthralgia, malaise, diarrhea, and fever of 101.6°F. Upon hospit al admission, she is found to be leukopenic. The patient continues to decompensate and dies 3 days following admission. A section of her right kidney taken at autopsy is shown in below figure. This figure indicates an infection with which of the following agents?

  

  A. cytomegalovirus

  B. Epstein-Barr virus

  C. Human immunodeficiency virus

  D. Pneumocystis carinii

  E. S. epidermidis

  F. Streptococcus pyogenes

  Correct Answer: A

  Section: Pathology and Path physiology Opportunistic infections can occur in posttransplant patients on immunosuppressive therapy. figure shows greatly enlarged renal tubular cells containing both nuclear and multiple cytoplasmic inclusion bodies. These findings in combination are diagnostic of cytomegalovirus infection. Epstein-Barr virus (choice B) has been associated with a number of diseases, including infectious mononucleosis, Burkitt lymphoma, and nasopharyngeal carcinoma. However, even though this is also a herpes virus, it does not give the morphologic appearance described. Human immunodeficiency virus (choice C) does not produce inclusion bodies in infected cells. P. carinii (choice D) is an opportunistic fungus that can cause pneumonia in immunocompromised individuals, particularly AIDS patients. It may be visualized with silver staining methods. S. epidermidis (choice E) and S. Pyogenes (choice F) are bacteria that one would not associate with this histologic appearance.

• Question 223:

  A 25-year-old woman discovers a breast lump during self-examination. On physical examination you identify a firm, round, movable, non-tender mass in the upper outer quadrant of the left breast. Your provisional diagnosis would be which of the following?

  A. carcinoma

  B. fibroadenoma

  C. fibrocystic change

  D. glandular hyperplasia

  E. liposarcoma

  Correct Answer: B

  Section: Pathology and Path physiology A single, firm, non-tender, freely movable breast mass in a woman of this age is most likely a fibroadenoma but, of course, this would need to be confirmed. These same factors make carcinoma (choice A) much less likely. Fibrocystic change (choice B) and glandular hyperplasia (choice D) would be expected to be bilateral rather than a single, isolated mass. Liposarcoma of the breast is very rare.

• Question 224:

  A 38-year-old woman has experienced the gradual onset of a goiter. Serum T4 and T3 are within the reference range and thyroid-stimulating hormone (TSH) is slightly increased. Serum antithyroid peroxidase (antimicrosomal) antibodies are detected but there are no TSH receptor antibodies. Which of the following is the most likely diagnosis?

  A. chronic autoimmune thyroiditis

  B. Graves disease

  C. primary atrophy of the thyroid

  D. riedel struma

  E. subacute thyroiditis

  Correct Answer: A

  Section: Pathology and Path physiology Patients with chronic autoimmune thyroiditis or Hashimoto disease may demonstrate several different serum thyroid autoantibodies, but these vary from patient to patient. Thyroid peroxidase antibodies are found in roughly 85% of patients with Hashimoto disease, about 40% of patients with Graves disease, and in <15% of patients with other thyroid disorders. The absence of TSH receptor antibodies rules out Graves disease (choice B), making Hashimoto disease the most likely diagnosis. Primary atrophy of the thyroid (choice C) and Riedel struma (choice D) are not usually associated with the formation of thyroid autoantibodies. Thyroid autoantibodies are only found transiently in a few patients with subacute thyroiditis (choice E) making this choice unlikely.

• Question 225:

  A 43-year-old man complains of a 25-lbs weight gain over the past 2 years distributed mostly in the trunk and face. He also states that he has developed abdominal stretch marks and facial acne during the same time period. Physical examination reveals BP 160/100 mm Hg and pulse 90 per minute. Significant laboratory tests were fasting glucose 145 mg/dL and 24-hour urinary free cortisol greatly increased at 390 g/d. The dexamethasone suppression test showed suppression of the urinary free cortisol at high but not low doses. Based upon this information, you would expect to find a hormonally- active tumor in which of the following sites?

  A. adrenal cortex

  B. adrenal medulla

  C. anterior pituitary

  D. posterior pituitary

  Correct Answer: C

  Section: Pathology and Path physiology This patient has the physical stigmata of excess cortisol or Cushing syndrome which is confirmed by the urinary free cortisol levels. Cortisol also has some mineralocorticoid activity producing sodium and water retention and hypertension. Cortisol promotes gluconeogenesis leading to glucose intolerance, hyperinsulinism and, in some patients, frank diabetes. The fact that urinary cortisol levels were suppressed by high but not low doses of dexamethasone strongly suggests a pituitary-based Cushing syndrome due to excess ACTH production or Cushing disease. ACTH-producing cells or corticotropes are found in the anterior pituitary. The dexamethasone suppression test rules out the adrenal (choices Aand B) as a site for the tumor and posterior pituitary (choice D) is not the location of the ACTH- producing cells.

• Question 226:

  A 76-year-old man with a long history of coronary artery disease presents to the emergency room with progressive substernal chest pain over the past 4 hours. He is short of breath and reports pain in his left jaw and shoulder area. His vital signs include blood pressure of 146/90 mm Hg, respiration rate of 20 per minute, pulse of 98 per minute, and normal temperature. An initial ECG demonstrates ST elevation changes and a baseline troponin I level of 2.8 ng/mL. He is admitted to the coronary care unit for treatment. Four hours post-admission, the patient reports having no chest pain or dyspnea and is resting comfortably. His vital signs are stable. Which of the following complications are you most concerned about occurring in this patient within the next 24 hours?

  A. cardiac tamponade

  B. cardiogenic shock

  C. holosystolic murmur

  D. systemic thromboembolism

  E. ventricular arrhythmia

  Correct Answer: E

  Section: Pathology and Path physiology The findings in this patient confirm the diagnosis of an acute MI. While all of the given choices are potential post-MI complications, they differ in incidence and temporality. Ventricular arrhythmias are the most common complication, occurring in >75% of cases; they typically arise in the first 3 days following an MI, but are especially frequent in the first 24 hours. Cardiac tamponade (choice A) can develop with rupture of the left ventricular free wall and is frequently fatal; although this is most likely to occur within the first 48 hours, incidence is far lower compared to arrhythmias (~ <10%). Cardiogenic shock (choice B) may occur at any time, either as an early post-MI event (24 hours) with large infarctions or secondary to later complications (37 days); however, incidence is estimated at roughly 10%, and patients suffering from early cardiogenic shock would have signs of hypotension and pulmonary edema. Post-MI holosystolic murmurs (choice C) may develop secondary to mitral valve regurgitation (infrequently, tricuspid valve regurgitation) stemming from rupture of a papillary muscle, or from potential rupture of the interventricular septum; these are both rare events (12%). Systemic thromboembolism (choice D) is a potential consequence of mural thrombus formation, which develops as a result of endocardial injury and stasis caused by poor myocardial contractility; incidence of both events is fairly common (2040%). Mural thrombi typically form within the first 12 weeks post-MI; systemic thromboemboli may occur at any point after formation of a mural thrombosis, and do not adhere to any particular time course.

• Question 227:

  A 12-year-old boy develops a large facial tumor. The histology of the lesion obtained from a fineneedle biopsy is displayed in below figure. The most likely diagnosis is which of the following?

  

  A. adenocarcinoma

  B. Burkitt lymphoma

  C. chronic lymphocytic leukemialymphoma

  D. parasitic lymphadenitis

  E. salivary gland lymphoepithelioma

  Correct Answer: B

  Section: Pathology and Path physiology The fine-needle biopsy shown in figure demonstrates a fairly monomorphic population of small, mitotically active neoplastic lymphocytes with associated starry sky histiocytes. The morphology of the tumor and the clinical history are typical for endemic Burkitt lymphoma. The diagnosis of adenocarcinoma (choice A) is incompatible with the photograph because malignant epithelial elements are not seen. Chronic lymphocytic leukemialymphoma (choice C) is distinctly uncommon in children and features mature lymphocytes without a starry sky background. There are no parasitic elements (choice D) evident in the photograph. Salivary gland lymphoepithelioma (choice E) is usually seen in an older age group, contains some remaining epithelial elements, and has larger immunoblastic-type lymphocytes.

• Question 228:

  An 81-year-old man who contracted syphilis while serving in World War II is now found to have a saccular aneurysm of the thoracic aorta. The pathogenesis of this lesion is best explained by which of the following?

  A. endarteritis obliterans of the vasa vasorum with subsequent mural ischemia

  B. hypersensitivity reaction with multinucleated giant cells and mural fibrinoid necrosis

  C. immune complex formation and complement activation

  D. intimal fibroplasia and lipid deposition

  E. medial cystic necrosis

  Correct Answer: A

  Section: Pathology and Path physiology Syphilitic saccular aneurysms of the thoracic aorta result from endarteritis obliterans of the vasa vasorum with subsequent mural ischemic necrosis. Hypersensitivity reactions, multinucleate giant cells, and fibrinoid necrosis (choice B) play no significant role in the development of syphilitic aortic aneurysms. Immune complex formation and complement activation (choice C) may be seen with tertiary syphilis, but involve only the small vessels, without aneurysm formation. Intimal fibroplasias and lipid deposition (choice D) are the early lesions of atherosclerosis. Cystic medial necrosis (choice E) is a noninfectious disorder characterized by abnormally weak connective tissue in the aortic media and deposits of myxoid substances.

• Question 229:

  An 89-year-old man develops a persistent cough with increasing dyspnea. He worked in the shipyards during his 20s, is a lifelong smoker, and has a positive purified protein derivative (PPD) skin test. During the physical examination, a pleural effusion is detected and subsequently drained. Laboratory analysis reveals a specific gravity of 1.013, protein of 1.4 g/dL, and a small number of macrophages. Based upon these laboratory values, which of the following is the most likely diagnosis for this patient?

  A. heart failure, left-sided

  B. heart failure, right-sided

  C. lung infection, bacterial

  D. lung infection, tuberculous

  E. primary malignancy, squamous cell

  F. primary malignancy, mesothelioma

  Correct Answer: A

  Section: Pathology and Path physiology Pleural effusion that has a specific gravity less than 1.012 and a protein concentration of less than 1.5 g/dL is classified as a transudate and is associated with circulatory problems (increased hydrostatic pressure, decreased oncotic pressure, lymphatic obstruction). Exudates usually have a specific gravity >1.020 and protein concentration higher than 3 g/dL and are associated with inflammatory or neoplastic processes. Based upon the laboratory results, the patient has a transudate which rules out infection (choices C and D) and neoplasms (choices E and F). The persistent cough and dyspnea indicate that the fluid is accumulating in his lungs, which occurs in left-sided heart failure. Apure right- side heart failure would be expected to produce a systemic rather than pulmonary edema.

• Question 230:

  A 23-year-old woman develops a sore throat, chills, headache, coryza, and a nonproductive cough. A chest x-ray reveals an indistinct, patchy interstitial infiltrate. She has an uneventful recovery within a few days without receiving therapy. Which of the following outcomes is most likely to occur in the region of the affected lung?

  A. healing by first intention

  B. metaplasia

  C. repair by scar formation

  D. resolution

  E. subacute inflammation

  Correct Answer: D

  Section: Pathology and Path physiology Resolution, or restoration of tissue to its preinjury state, occurs in tissue injury where minimal cell necrosis has occurred, such as this case of interstitial pneumonia. Removal of debris associated with the accompanying acute inflammatory response is sufficient to restore parenchymal tissue to its normal state. Regeneration of new parenchymal cells will occur to replace necrotic cells provided the involved cells have:

  (i) regenerative capacity; (ii) exist in remaining sufficient viable number, and (iii) possess an adequate connective tissuesupporting framework. Healing by first intention (choice A), also known as primary union, describes healing of skin wounds in which the edges are in close apposition, such as a surgical incision. Metaplasia (choice B), the replacement of one mature cell type by another mature cell type abnormal to that location, occurs most commonly in epithelial tissues where chronic physical or chemical irritation is present, such as squamous metaplasia of the endocervix or bronchial mucosa, and intestinal metaplasia of the esophagus. Repair by scar formation (choice C) occurs either in injured tissue comprised of permanent cells (e.g., myocardium), when resolution fails to occur in acute inflammation, or if chronic inflammation persists with ongoing necrosis. Subacute inflammation (choice E) describes repeated attacks of acute inflammation in which incomplete resolution of individual attacks leads to increasing chronic inflammation with superimposed acute inflammation.