Myelodysplastic syndrome in two young brothers

We report the youngest cases of myelodysplastic syndrome (MDS) in two brothers aged 7 and 2 years. The maternal grandfather and maternal grandmother had been exposed to radioactive fallout after the atomic bomb attack on Hiroshima in 1945. The elder brother demonstrated pancytopenia with < 1% blast cells in his peripheral blood and < 5% in his bone marrow at diagnosis. The younger brother was thrombocytopenic without increased blasts. The karyotype of bone marrow cells from the elder brother was 46,XY, -7, +der (7), t(1:7) (lqter-lq11::7q11-7pter), but the younger brother's karyotype was normal. Immature myeloid cells in the bone marrow from both brothers were morphologically abnormal. A diagnosis of refractory anaemia (RA) was made in both brothers. Atavism due to radioactive poisoning was suspected in the development of MDS in these two cases.