Thrombotic thrombocytopenic purpura (TTP) is caused by deficiency of which enzyme, leading to accumulation of ultra-large von Willebrand factor multimers?

• A Complement factor H regulating the alternative complement pathway
• B Protein C, the anticoagulant serine protease
• C Factor VIII–von Willebrand factor cleaving protease (ADAMTS13) ✓
• D Thrombomodulin, the endothelial cell receptor for thrombin

Explanation

TTP results from severe deficiency of ADAMTS13 (a plasma metalloprotease), either inherited (Upshaw-Schulman syndrome) or from acquired inhibitory antibodies. ADAMTS13 normally cleaves ultra-large vWF multimers released by endothelial cells; without it, these multimers persist in the circulation, binding platelets and forming microthrombi in small vessels — causing the pentad of thrombocytopenia, MAHA, fever, renal dysfunction, and neurological symptoms.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.