Acquired Immune Thrombotic Thrombocytopenic Purpura Following Transaxillary Transcatheter Aortic Valve Replacement: A Rare Life-Threatening Hematologic Emergency.

Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening complication of transcatheter aortic valve replacement (TAVR). Because early thrombocytopenia after TAVR is common and usually benign, iTTP may be overlooked. An 87-year-old man underwent successful transaxillary TAVR. His platelet count fell from 210 to 16×10³/µL within 72 hours, with hemoglobin declining from 9.5 to 6.8 g/dL. There were no bleeding, neurological, or renal manifestations. Laboratory findings were consistent with microangiopathic hemolytic anemia, and ADAMTS13 activity was <1% (French score 3), confirming iTTP. Treatment with plasma exchange, corticosteroids, caplacizumab, and rituximab led to rapid platelet recovery. The diagnosis of iTTP should be considered in patients presenting with unexplained thrombocytopenia and hemolysis after TAVR, even when asymptomatic. Early recognition and prompt initiation of therapy are essential to improve outcomes.