Persistent remission after immunosuppressive therapy of hairy cell leukemia mimicking aplastic anemia: two case reports.

Some patients with hairy cell leukemia (HCL) manifest pancytopenia and bone marrow hypoplasia without an apparent increase in atypical cells, so their disease resembles severe aplastic anemia at onset. We treated 2 HCL patients, who were initially diagnosed with aplastic anemia, with antithymocyte globulin (ATG) in combination with cyclosporine or antilymphocyte globulin (ALG). Both patients obtained partial remission in response to the immunosuppressive therapy and did not need transfusion treatment for more than 3 years. Sustained improvement of hematopoiesis in such B-cell malignancies after ATG/ ALG therapy suggests that the mechanisms underlying successful immunosuppressive therapy for aplastic anemia may involve B-cell suppression, inhibiting hematopoietic stem cells.