[Radiation-induced hematopoietic disorders]

Hematopoietic stem cells are one of the most sensitive tissues to radiation exposure. Epidemiological studies of atomic bomb survivors in Nagasaki and Hiroshima revealed a radiation dose-response relationship for acute myeloid leukemia, acute lymphoblastic leukemia, and Chronic myelogenous leukemia. In our study of myelodysplastic syndrome (MDS) in Nagasaki, the relative risk was higher in the proximal-exposed group. Additionally, the frequency of chromosome abnormalities associated with poor prognosis was higher in the proximal-exposed group than in the non-exposed group. However, no association between the exposure distance and prognosis was observed. We used next-generation sequencing to analyze the role of genetic abnormalities in the development of MDS. The results indicated that genetic mutations related to DNA methylation pathways, which are frequently observed in de novo MDS, were considerably less frequent in the proximal-exposed than in the distal-exposed group. These results suggest that the pathogenesis of MDS in atomic bomb survivors may be different from that of treatment-related and de novo MDS.