Isolated thrombocytopenia after allogeneic bone marrow transplantation: Existence of transient and chronic thrombocytopenic syndromes

Abstract

Isolated thrombocytopenia after bone marrow transplantation was investigated in 65 fully engrafted patients surviving at least 60 days posttransplant. Twenty-four patients (37%) developed this complication, which occurred most frequently in patients receiving pretransplant preparation with total body irradiation or busulfan. Two distinct thrombocytopenic syndromes were identified: (1) transient thrombocytopenia (9 patients), in which a normal platelet count (>100,000/μL) was initially established by day +40 but then diminished to <10,000 to 45,000/μL on day +40 to +70, with subsequent resolution of the thrombocytopenia by day +90; (2) chronic thrombocytopenia (15 patients), in which a platelet count >100,000 μL was not achieved at any time during the first 4 months posttransplant, despite the simultaneous presence of normal granulocyte and reticulocyte counts. Although the transient syndrome did not adversely affect prognosis, the chronic syndrome carried a high mortality (21% actuarial survival at 1,000 days posttransplant compared with 67% survival for all patients, P < .01) and had a high association with both severe (grades 3 to 4) acute graft-versus-host disease (GVHD) and chronic GVHD. In 3 of 9 patients with transient thrombocytopenia, a temporal association with trimethoprim-sulfamethoxazole administration was observed, whereas in all other patients, no drug association could be found. Bone marrow biopsies in those patients with drug-associated thrombocytopenia showed decreased numbers of megakaryocytes, whereas biopsies in the remainder of the transiently thrombocytopenic patients demonstrated adequate numbers of platelet precursors, suggesting peripheral platelet destruction or ineffective thrombopoiesis. Biopsies in the chronic thrombocytopenic patients included those with and without adequate numbers of platelet precursors, although the association with chronic GVHD was strongest in patients demonstrating normal numbers of megakaryocytes. We conclude that isolated thrombocytopenia represents a significant complication of bone marrow transplantation, particularly in patients receiving hematopoietic ablative preparatory regimens, and that it is the chronic, not the transient, thrombocytopenic syndrome that is associated with an adverse patient prognosis.