Acquired amegakaryocytic thrombocytopenia (AAT) is a rare hematological disorder causing severe thrombocytopenia and bleeding. Previous in vitro studies postulated both cell-mediated suppression of megakaryocytopoiesis in early megakaryocytic progenitor cells and humoral-mediated suppression by anti-thrombopoietin antibodies as possible etiologies of AAT. Patients with AAT usually present with severe bleeding and thrombocytopenia that is unresponsive to steroids and intravenous immunoglobulin (IVIG). Although standard guidelines have not been established for management of AAT, a few case reports have indicated a response to immunosuppressive treatment. The prompt recognition of this disease entity is essential in view of the substantial risk of morbidity and mortality from excessive bleeding. We report a case of AAT successfully treated with equine antithymocyte globulin (ATG) and cyclosporine (CSP). 1. Case Presentation A 40-year-old woman with a past medical history of migraine headaches presented to her primary care physician with the chief complaint of “I am almost bleeding to death” and endorsed a history of fatigue, easy bruising, and frequent nosebleeds. Her only medication was an oral contraceptive. A complete blood count (CBC) revealed a platelet count of /L (normal, /L), and she was referred to a hematologist. She was initially diagnosed with idiopathic thrombocytopenia purpura (ITP) and was treated with prednisone 60？mg per day for one week, without improvement in platelet count. A bone marrow biopsy (BMB) revealed a hypercellular marrow (75%) with trilineage hematopoiesis but with decreased megakaryocytes; maturation of erythroid and myeloid elements were normal. Because of persistent thrombocytopenia, her treatment regimen was modified to include weekly platelet infusions and prednisone. After each platelet transfusion, there was an increment in platelet level from approximately /L to approximately /L, followed by a return to baseline level of approximately /L over the following 2-3 days. The patient was then referred to our hematology service for further evaluation. On physical examination, she had scattered petechiae and ecchymosis on her upper and lower extremities, but no rashes, hepatosplenomegaly, or lymphadenopathy. A CBC showed a platelet count of /L, and review of the peripheral blood smear showed rare giant platelet forms and the absence of platelet clumps. In addition, a leukocytosis was present with a white blood cell count of /L (normal, /L), with absolute neutrophil count (ANC) of /L (normal, /L), and with an absolute
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