USMLE PRACTICE QUESTION OF THE WEEK

Question for September 26, 2025

A 48-year-old woman presents with confusion, blurred vision, and weakness. She has a history of systemic lupus erythematosus. Blood pressure is 160/95 mmHg, temperature 37.0°C.

Laboratory results:
  • Platelet count: 45,000/mm³
  • Hemoglobin: 7.5 g/dL
  • Creatinine: 2.5 mg/dL (baseline 0.9 mg/dL)
  • LDH: 850 U/L (normal 100-250 U/L)
  • Peripheral smear: Schistocytes present
Which of the following is the best immediate next step in management?

Correct Answer:

B. Plasmapheresis

Correct Answer Explanation

The patient has thrombotic thrombocytopenic purpura (TTP) presenting with microangiopathic hemolytic anemia (schistocytes, elevated LDH), thrombocytopenia, neurologic symptoms, and renal dysfunction. Immediate plasmapheresis is life-saving, removing ADAMTS13 autoantibodies and preventing mortality that exceeds 90% without treatment.

Why These Are Incorrect:

  • A. Contains ADAMTS13 but insufficient without removal of inhibitory antibodies.
  • C. Contraindicated - worsens bleeding risk without addressing underlying pathophysiology.
  • D. Used as adjunctive therapy but never replaces urgent plasmapheresis.
  • E. Causes megaloblastic anemia with hypersegmented neutrophils, not schistocytes.