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Some allogeneic stem cell transplantation (allo-SCT) recipients develop therapy-related myeloid neoplasms (t-MNs) of recipient origin with features including karyotypically abnormal hematopoiesis without cell dysplasia and myeloblast increase. However, due to their rarity their clinical course remains unclear. We report six cases of t-MN in patients with chromosomal abnormalities (CAs) after autologous recovery following allo-SCT for acute leukemia. CAs were first detected at a median interval of 422 (range 30-1941) days from allo-SCT. The fraction of CA-bearing cells of recipient origin increased with time, and cytogenetic relapse of underlying disease was not observed. Continuous emergence of identical autologous CAs was observed in one patient who did not receive total body irradiation (TBI). The other five patients received TBI, and complex karyotypes with the appearance of different types of CAs were the most dominant feature. Despite the persistence of complex abnormalities in the irradiated patients, no patient developed therapy-related acute myeloid leukemia (t-AML). TBI appears to be the major cause of t-MN of recipient origin with different types of CAs. Although t-MNs in patients receiving TBI do not initially seem to evolve to overt t-AML, they were associated with higher risk of underlying disease and greater oncogenic potential of irradiation.

Some patients with thrombotic thrombocytopenic purpura (TTP) are refractory to standard treatment regimens comprised of plasma exchange (PEX) and steroids. This report describes a 40-year-old woman with refractory TTP who achieved complete remission (CR) in response to rituximab. She was referred to our institution from a rural hospital with purpura of the extremities, severe thrombocytopenia, anemia, and rapidly progressive disturbance of consciousness. TTP was diagnosed based on the clinical symptoms of TTP, low ADAMTS13 activity (0.5%), and high ADAMTS13 inhibitor (4.4 BU/ml) titers. High-dose prednisolone was immediately administered and PEX was started. This approach was initially effective, but the thrombocytopenia and disturbance of consciousness worsened on the sixth day of treatment. We considered this patient to have refractory TTP and administered weekly rituximab. CR was achieved on day 20, and the disease status of this patient has remained stable over the long term. Our experience with this patient and five others who were similarly treated at our hospital over the past eight years indicates that rituximab is effective for refractory TTP.