Acquired ADAMTS13 inhibitor causing thrombotic thrombocytopenic purpura (TTP) may be precipitated by some infections, inflammatory diseases or neoplasia. We reported a case of refractory TTP precipitated by a newly diagnosed localized Castleman's disease (CD). TTP was initially treated with plasma exchange and immunosuppressive therapy with corticosteroids; however the treatment failed to promote sustained response. During hospitalization, an abdominal tumor was diagnosed and resected; the histological analysis revealed a CD of hyaline-vascular variant rich stroma. After tumor removal, the patient achieved a long-lasting clinical remission and normalized ADAMTS13 activity. This clinical case describes a novel association of acquired ADAMTS13 inhibitor and CD. The antibody to ADAMTS13 developed along with the systemic manifestation of CD and promptly disappeared after the resection of the tumor. There are reports of neoplasia-associated thrombotic microangiopathy however direct evidence of CD-dependent ADAMTS13 inhibitor had not yet been reported.263 263266