Anemias USMLE Step 1 Practice Question
A 67-year-old man comes to the office in winter because of fatigue and dark urine. He reports that his fingers become painful and bluish when he walks outside in the cold. Laboratory studies show anemia and elevated indirect bilirubin. Direct antiglobulin testing is positive for complement. Which of the following is the most likely etiology of this patient's hemolysis?
Answer choices
- AShiga toxin-mediated endothelial injury
- BIgG antibodies directed against Rh antigen
- CIgM antibodies binding erythrocytes at low temperaturesCorrect answer
- DOxidative denaturation of hemoglobin due to low glutathione
- EDeficiency of spectrin in the red cell membrane
- FParoxysmal cold hemoglobinuria
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