Preleukemic states in atomic bomb survivors in Japan

Cytologic and cytogenetic studies were performed on the bone marrow cells in atomic bomb-exposed patients who had prolonged periods of blood disorders with termination of acute leukemia (group I, 6 cases) and without the termination (group II, 6 cases), and survivors who were in apparent good health (group III, 85 cases). All but one patient in group I, who were examined at the preleukemic state, had abnormal clones. In 4 out of 6 of group I patients, morphologic abnormalities of bone marrow cells taken 3-10 years before leukemic development were found, such as giant neutrophils or basophils, binucleated granulocytes or megakaryocytes, and bridge formation of chromatid in metaphases. All patients in group II had stable types of chromosome aberrations. The types of cytologic abnormalities were similar to those in group I, but the frequencies were a little less than those in group I. In group III, 14 persons were found to have stable types of chromosome aberrations, of which 11 persons had apparent but transient clone formations. Cytologic and clinical abnormalities were not observed in the group. The persistent and high percentages of cytologic and cytogenetic abnormalities in patients with prolonged periods of blood disorders, regardless of history of radiation exposure, would suggest a preleukemic state, and also give some clue to the problems of leukemogenesis.