Successful Treatment of Acquired Amegakaryocytic Thrombocytopenia with Rituximab: A Case Report.

Abstract 4223

Acquired amegakaryocytic thrombocytopenia is a rare disorder in which there is a marked decrease in bone marrow megakaryocytes leading to severe thrombocytopenia with preserved hematopoeisis in the remaining lineages. The clinical course is variable and no standardized treatment exists. Multiple cases in the literature report treatment using immunosuppressive agents including cyclosporine and antithymocyte globulin. In this case report, we describe the first successful use of rituximab in a patient with amegakaryocytic thrombocytopenia in the absence of any underlying autoimmune disorders. Our patient, an 86- year-old woman, presented with epistaxis, ecchymoses, and blood-tinged sputum. She had thrombocytopenia (platelets 6 × 10⁹/L, MPV 8.3) with a normal hemoglobin and white blood cell count. Peripheral blood smear showed no obvious cause for thrombocytopenia. Bone marrow biopsy revealed focal lymphocytic infiltrates and severe megakaryocytic hypoplasia with nearly absent megakaryocytes. Cytogenetic and molecular analyses were normal, revealing no evidence of a clonal myelo- or lymphoproliferative disorder. The diagnosis of amegakaryocytic thrombocytopenia was made. She was started on prednisone 50mg per day. There was no significant improvement in her platelet count and she was then given IVIG without response. Repeat bone marrow biopsy showed persistent severe bone marrow hypoplasia with near absence of megakaryocytes. After 6 weeks of platelet transfusion dependence and steroids, she was tapered off her steroids and was given rituximab 375mg/m2 weekly for 4 doses. Three weeks after starting rituximab, her platelet counts began to recover and by day 37, her platelet counts normalized and remained within normal limits 12 months after treatment. This case demonstrates the possible utility of rituximab in treating patients with isolated acquired amegakaryocytic thrombocytopenia.