A 30-year-old woman is 28 weeks pregnant and develops thrombocytopenia (platelets 45,000/µL), microangiopathic hemolytic anemia, and fever. Serum ADAMTS13 activity is <10% with a high-titer inhibitor. Which diagnosis is confirmed and what is the immediate treatment?
- A Pre-eclampsia with HELLP syndrome — treatment is delivery
- B Congenital TTP (Upshaw-Schulman syndrome) — treatment is fresh frozen plasma infusion only
- C Complement-mediated HUS — treatment is eculizumab
- D Acquired thrombotic thrombocytopenic purpura (TTP) due to ADAMTS13 autoantibody — immediate plasma exchange (PEX) + caplacizumab + immunosuppression ✓
Explanation
ADAMTS13 activity <10% with a high-titer inhibitory autoantibody confirms acquired (immune-mediated) TTP. ADAMTS13 normally cleaves ultra-large von Willebrand factor (ULVWF) multimers; its deficiency allows ULVWF to accumulate, causing platelet-rich microthrombi in the microvasculature with MAHA and thrombocytopenia. Treatment: immediate plasma exchange (replacing ADAMTS13 + removing inhibitor) + rituximab (targeting B cells producing the antibody) + caplacizumab (anti-vWF nanobody that rapidly reduces thrombus formation and is now standard per HERCULES trial). HELLP lacks the severe ADAMTS13 deficiency; congenital TTP has no inhibitor; complement-HUS shows ADAMTS13 >10%.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.