A 45-year-old man presents with a hemoglobin of 7.2 g/dL, MCV 72 fL, raised LDH, reduced haptoglobin, raised indirect bilirubin, peripheral smear showing schistocytes (3%), and a direct Coombs test that is negative. ADAMTS13 activity is <5%. Platelets are 28,000/µL. Creatinine 2.8 mg/dL. What is the immediate treatment?
- A Platelet transfusion + corticosteroids
- B Plasma exchange (therapeutic plasma exchange — TPE) + caplacizumab ✓
- C Eculizumab (anti-C5 complement inhibitor)
- D Steroids + rituximab
Explanation
ADAMTS13 activity <10% is diagnostic of immune-mediated thrombotic thrombocytopenic purpura (iTTP), characterized by MAHA (schistocytes, negative Coombs), thrombocytopenia, and organ dysfunction. TTP is a medical emergency with >90% mortality if untreated. Immediate treatment is therapeutic plasma exchange (TPE) — daily TPE until platelet count >150,000 for 2 consecutive days, replacing inhibitory ADAMTS13 antibodies and replenishing enzyme. Caplacizumab (anti-vWF nanobody) is added to reduce acute TTP-related deaths and recurrence per HERCULES trial. Platelet transfusion is contraindicated — it 'fuels the fire' by providing substrate for further microvascular thrombosis. Eculizumab is for aHUS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.