A 40-year-old woman has microangiopathic haemolytic anaemia (MAHA), thrombocytopenia (platelet 18,000), normal PT/aPTT, elevated LDH, and elevated creatinine 2.6 mg/dL. Peripheral smear shows schistocytes. ADAMTS13 activity is 8% (normal >67%). Which diagnosis is confirmed and what is the FIRST treatment?

• A Haemolytic uraemic syndrome (HUS) — supportive care and eculizumab
• B DIC — fresh frozen plasma and cryoprecipitate
• C HELLP syndrome — delivery of fetus
• D Thrombotic thrombocytopenic purpura (TTP) — urgent plasma exchange (TPE) ✓

Explanation

ADAMTS13 activity <10% confirms immune-mediated TTP (iTTP), caused by autoantibodies against ADAMTS13 (von Willebrand factor cleaving protease), leading to platelet microvascular thrombi and MAHA. Plasma exchange (TPE) is the cornerstone of treatment as it removes the inhibitory antibodies and replenishes ADAMTS13. Eculizumab is for atypical HUS (complement-mediated), which has normal/near-normal ADAMTS13. DIC has low PT/aPTT prolongation. HELLP occurs in pregnancy.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.