Successful treatment with azathioprine for autoimmune thrombocytopenia developing after autologous peripheral blood stem cell transplantation

A 60-year-old man with acute promyelocytic leukemia in complete remission had minimal residual disease (MRD). After two courses of arsenic trioxide treatment, the MRD disappeared. In October 2005, he received an unmanipulated autologous peripheral blood stem cell transplantation (autoPBSCT). Hematologic recovery was prompt; however, after day 21 following the autoPBSCT, platelet counts decreased to below 10 x 10(9)/l. A bone marrow aspirate showed an increased number of immature megakaryocytes, and platelet-associated IgG was elevated to 48.5 ng/10(7) platelets. A diagnosis of autoimmune thrombocytopenia was made. The combination of oral prednisolone (40 mg/day) and bolus immunoglobulin infusion (400 mg/kg, for 5 consecutive days) was ineffective. He was given azathioprine (50 mg/day, orally), and 10 days after the initiation of the treatment, the platelet counts gradually increased and recovered to over 50 x 10(9)/l on day 168, and 100 x 10(9)/l on day 364. To the best of our knowledge, successful treatment of ITP following auto PBSCT with azathioprine has not been previously reported.