Thrombotic thrombocytopenic purpura (TTP) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ dysfunction. The primary pathogenetic mechanism is:

• A Anti-platelet antibodies causing immune-mediated platelet destruction (similar to ITP)
• B Complement-mediated destruction of red blood cells and platelets via alternative pathway
• C Consumption of coagulation factors and platelets in widespread fibrin thrombi (DIC pattern)
• D Deficiency or inhibition of ADAMTS13, preventing cleavage of ultra-large von Willebrand factor multimers that cause platelet thrombi in microvasculature ✓

Explanation

TTP is caused by severe deficiency of ADAMTS13 (a von Willebrand factor-cleaving metalloprotease), either acquired (autoantibody-mediated inhibition) or hereditary (Upshaw-Schulman syndrome). Uncleaved ultra-large VWF multimers tether platelets in the microvasculature, forming platelet-rich thrombi that cause MAHA and thrombocytopenia. Unlike DIC, coagulation times (PT/aPTT) are typically normal in TTP.

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

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Written and medically reviewed by the StethoPrep medical team.