Purpose : Genetic alterations, including microsatellite instability (MSI), are ultimate steps toward malignant process. To investigate MSI in A-bomb survivors, leukaemic cells were analysed from 13 acute myelocytic leukaemia patients with a history of radiation exposure and also in 12 de novo patients.

Materials and methods : To assess the microsatellite changes, a fluorescent system in 10 loci (BAT40, D3S643, D5S107, IRF1, MYC, D9S171, WT1, TP53, DM, D17S855) was used.

Results : MSI analysis revealed a high frequency of multiple microsatellite changes in the exposed patients (84.6%) compared with non-exposed patients (8.3%). There was a significant difference ( p <0.001) between the two groups.

Conclusions : These analyses clearly demonstrate that leukaemic cells from heavily exposed patients contain a number of genetic instabilities that may strongly influence the development of leukaemia among people exposed to the Hiroshima A-bomb radiation.