[Successful treatment with cyclosporine in a patient with rituximab-refractory thrombocytopenic purpura].

Acquired thrombotic thrombocytopenic purpura (aTTP) is a life-threatening systemic thrombotic microangiopathy characterized by the presence of anti-ADAMTS13 antibodies (inhibitor). Here we report the case of a patient with refractory aTTP successfully treated with cyclosporine. A 69-year-old man presenting with hematuria and petechiae was referred to our hospital; he was disoriented and febrile. Laboratory results revealed Coombs-negative hemolytic anemia, thrombocytopenia, and renal failure. Undetectable ADAMTS13 activity and presence of anti-ADAMTS13 antibodies (inhibitor) confirmed the diagnosis of aTTP. Despite performing plasma exchange and administering prednisolone and rituximab (375 mg/m2), we were unable to restore his platelet counts to the normal level. Therefore, he was treated with cyclophosphamide (500 mg/bodyweight), vincristine (1.4 mg/m2), bortezomib (1.3 mg/m2), and cyclosporine (2.5 mg/kg). After the cyclosporine therapy, his platelet counts gradually normalized. Continuous cyclosporine maintenance therapy led to complete disappearance of the inhibitor. Therapeutic strategies for refractory aTTP have not yet been established. Further investigations are warranted to establish a therapeutic strategy for refractory aTTP.