Anemias USMLE Step 1 Practice Question
A 34-year-old man presents with episodic dark urine, fatigue, and abdominal pain. Vital signs show BP 118/76, HR 92, RR 16, temp 37.2°C, SpO2 98%. Laboratory studies reveal intravascular hemolysis with elevated LDH (680 U/L) and low haptoglobin (8 mg/dL). Abdominal imaging demonstrates hepatic vein thrombosis. Flow cytometry shows absent CD55 and CD59 on blood cells. He denies recent infections or medication use. Which of the following is the most likely underlying mutation?
Answer choices
- AMutation of spectrin leading to membrane instability
- BPIGA mutation impairing glycosylphosphatidylinositol anchor synthesisCorrect answer
- CBCR ABL fusion in a hematopoietic stem cell
- DMutation causing beta globin polymerization
- EJAK2 activating mutation in a myeloid progenitor
- FMutation in the ADAMTS13 gene reducing von Willebrand factor-cleaving protease activity
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.