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USMLE STEP2 Exam
Step2 (Page 24 )

Updated On: 1-Feb-2026
Page 24 of 149
PDF with 738 Questions

A 30-year-old woman comes to your office for evaluation of fatigue and shortness of breath on exertion. Past medical history is unremarkable. Physical examination is remarkable only for mild pallor. Lung and cardiovascular examination are normal. Laboratory tests show a hematocrit of 28 with a mean corpuscular volume of 72. WBC count and platelet count are normal. On taking further history from the patient, which of the following patient questions would most likely confirm a diagnosis?

  1. What is your family history of colon cancer?
  2. What is your family history of heart disease?
  3. How much alcohol do you drink?
  4. Do you have attacks of pain in your joints?
  5. How heavy are your menstrual periods?

Answer(s): E

Explanation:

Iron-deficiency anemia characteristically is a hypochromic, microcytic anemia. Causes of iron- deficiency anemia include menstrual loss, inadequate diet, malabsorption, chronic inflammation, and chronic blood loss. Colon cancer could lead to chronic blood loss and irondeficiency anemia. This, however, would be very uncommon in a young patient without a family history of colon cancer.
Alcohol causes a macrocytic anemia.



A 54-year-old man complains of cough, shortness of breath, and pleuritic left-sided chest pain. Examination and CXR are compatible with a large left-sided pleural effusion. At thoracentesis, the pleural fluid is straw colored and slightly turbid, with a WBC count of 53,000/mL, RBC count of 1200/mL, glucose of 42 mg/100 mL, total protein of 5 g/100 mL, LDH of 418 IU/L, and pH of 7.2. Simultaneous serum total protein is 8 g/100 mL (normal, 68 g/100 mL), and serum LDH level is 497 IU/L (normal, 52149 IU/L). Gram stain is positive for gram-negative rods.

Which of the following is the most likely cause of his pleural effusion?

  1. parapneumonic effusion
  2. congestive heart failure
  3. malignant effusion
  4. trauma
  5. nephrotic syndrome

Answer(s): A

Explanation:

Although the differential diagnosis of a pleural effusion is large, the diagnostic possibilities may be narrowed by classifying the fluid as transudative or exudative. Exudates are characterized by a pleural fluid- to-serum protein ratio greater than 0.5, pleural fluid LDH greater than 200 IU/L, or pleural fluid- toserum LDH ratio greater than 0.6. Other common findings in exudative effusions are a WBC count greater than 1000/mL, glucose less than 60 mg/100 mL, and grossly hemorrhagic fluid. Causes of transudative effusions include CHF, nephrotic syndrome, cirrhosis with ascites, and myxedema. Causes of exudative fluid include parapneumonic effusion, neoplasm, pulmonary infarction, tuberculosis, and fungal infection among others. Alow pleural fluid pH (<7.30) limits the differential diagnosis to empyema, carcinoma, collagen vascular disease, esophageal rupture, tuberculosis, or hemothorax. Uncomplicated parapneumonic effusions have WBC counts under 40,000/mL, normal glucose levels, and a pH under 7.30; a positive Gram stain or culture constitutes a complicated parapneumonic effusion. These tend to loculate and form adhesions if not immediately and thoroughly drained by chest tube placement.



Ayoung woman with a history of seizures has a series of grand mal seizures in the emergency room. She is lethargic and has a nonfocal neurologic examination. Her blood gas reveals a pH of 7.12, carbon dioxide of 48, PO2 of 86, and calculated bicarbonate of 16. How would you best characterize her underlying acid- base problem?

  1. respiratory acidosis
  2. metabolic and respiratory acidosis
  3. metabolic acidosis and respiratory alkalosis
  4. metabolic alkalosis and respiratory acidosis
  5. metabolic acidosis

Answer(s): B

Explanation:

The pH is 7.12, indicating acidosis as the primary disorder. Alow bicarbonate is consistent with a metabolic cause of the acidosis and a high carbon dioxide is consistent with a respiratory cause of the acidosis.
Therefore, both are contributing as primary problems. The metabolic source likely is lactic acidosis from muscle breakdown resulting from the seizures. The respiratory source likely is related to the patient's postictal state and hypoventilation after the seizures.



A 43-year-old man with AIDS complains of shortness of breath and worsening diarrhea. His temperature is 98°F, respiration rate is 26/min, pulse rate is 100 /min, and BP is 100/70 mmHg. His lung and heart examination are unremarkable. A room air ABG reveals: pH 7.10/PCO2 5/PO2 130/calculated bicarbonate
6. What is the primary acid-based disorder?

  1. respiratory acidosis
  2. respiratory alkalosis
  3. metabolic acidosis
  4. metabolic alkalosis

Answer(s): C

Explanation:

The pH is 7.10, which indicates the primary disorder to be an acidosis. The low bicarbonate and the low carbon dioxide both are indicative of a metabolic cause for the acidosis. For the primary cause of the acidosis to be respiratory, the carbon dioxide would need to be greater than 40. In this case, the patient is compensating for the metabolic acidosis due to chronic diarrhea by hyperventilation.



A 17-year-old girl notes an enlarging lump in her neck. On examination, her thyroid gland is twice the normal size, firm to rubbery, multilobular, nontender, and freely mobile. There is no adenopathy. Family history is positive for both hypo- and hyperthyroidism. Her serum triiodothyronine (T3) and thyroxine (T4) levels are low normal, and serum thyroid-stimulating hormone (TSH) is high normal. Technetium scan shows nonuniform uptake. Serum and antithyroglobulin titer is strongly positive.

What will thyroid biopsy of this patient most likely disclose?

  1. giant cell granulomas and necrosis
  2. polymorphonuclear cells and bacteria
  3. diffuse fibrous replacement
  4. lymphocytic infiltration
  5. parafollicular cells

Answer(s): D

Explanation:

The patient described in the question most likely has Hashimoto's thyroiditis, also called autoimmune or chronic lymphocytic thyroiditis. It is the most common cause of thyroiditis in the United States and is encountered more frequently in women than in men. Patients note progressive thyromegaly but are usually euthyroid at the outset. Hypothyroidism may appear years later, often heralded by an elevated serum TSH level. Diagnosis is based on the history, examination, heterogeneous uptake on thyroid scan, and the presence of antithyroid and antithyroglobulin antibodies. If the diagnosis is still in doubt, needle biopsy will demonstrate lymphocyte infiltration, sometimes in sheets or forming germinal centers. Subacute (de Quervain, granulomatous) thyroiditis will show polymorphonuclear cells, necrosis, and giant cells. Bacteria may not be present in acute suppurative thyroiditis. Thyroid infiltration and replacement by rock-hard, woody, fibrous tissue is typical of Riedel's struma. C-cell hyperplasia is associated with medullary thyroid carcinoma. Hashimoto's thyroiditis is treated with thyroid hormone. Lower doses (0.100.15 mg/day) of levothyroxine are used to treat hypothyroidism alone; whereas, higher doses (0.150.30 mg/day) suppress TSH release and diminish goiter size. Partial resection may result in enlargement of the remaining gland.
Steroids, antibiotics, and radioiodine have no role in therapy.



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