A 30-year-old woman presents with thrombocytopenia, microangiopathic hemolytic anemia, and neurological symptoms (confusion, seizures). Renal function is relatively preserved. LDH is markedly elevated; direct Coombs test is negative. What is the deficient or defective factor in the most common form of this condition?

• A Von Willebrand factor (vWF multimer cleavage protein)
• B Complement factor H (CFH)
• C Complement factor I (CFI)
• D ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin motifs 13) ✓

Explanation

Thrombotic thrombocytopenic purpura (TTP) presents with the pentad of microangiopathic hemolytic anemia, thrombocytopenia, fever, neurological abnormalities, and renal dysfunction (though neurological predominance distinguishes TTP from HUS). The pathophysiology involves ADAMTS13 deficiency — either acquired (autoantibody-mediated, immune TTP) or hereditary (Upshaw-Schulman syndrome). ADAMTS13 cleaves ultra-large von Willebrand factor (UL-vWF) multimers released from endothelium; its absence leads to UL-vWF accumulation, platelet-rich microvascular thrombi, and organ ischemia. Treatment is plasma exchange (provides ADAMTS13). Complement factor H/I deficiency causes atypical HUS with predominantly renal involvement.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.