Severe Immune-Mediated Thrombotic Thrombocytopenic Purpura With High-Titer ADAMTS13 Inhibitors: A Case Report.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening thrombotic microangiopathy caused by severe ADAMTS13 deficiency secondary to inhibitory autoantibodies. Prompt recognition and early initiation of treatment are essential to prevent irreversible organ damage and death. We report the case of a 46-year-old man who presented with constitutional symptoms, cutaneous purpura, severe thrombocytopenia, and microangiopathic hemolytic anemia. A PLASMIC score of 7 indicated a high probability of severe ADAMTS13 deficiency, which was confirmed by undetectable ADAMTS13 activity and high-titer inhibitory antibodies. The patient received therapeutic plasma exchange, corticosteroids, caplacizumab, and rituximab, resulting in rapid hematologic remission. An extensive diagnostic workup excluded alternative thrombotic microangiopathies. This case highlights the importance of early clinical recognition, systematic exclusion of alternative thrombotic microangiopathies, and prompt initiation of multimodal therapy in patients with suspected iTTP. It also illustrates the potential value of serial monitoring of ADAMTS13 activity and inhibitor titers as complementary biomarkers for assessing immunologic response and guiding therapeutic management.