Higher frequency of 51--clone in bone marrow mitoses after culture than by a direct method.

In a patient with refractory idiopathic sideroblastic anaemia without signs of leukaemia a clone with the karyotype 46,XX,5q--showed markedly different frequencies in mitotic preparations obtained from bone marrow by different methods. This clone was absent or rare (0--15%) in preparations made by a direct method and prevalent (55--95%) after culture for 22 h or 46 h in the presence or absence of methotrexate. In cells without the 51--chromosome there were minor clones with trisomies 8, 14 or 19. These were somewhat more frequent in preparations made by the methotrexate than by the direct method. If these findings are confirmed in larger series of experiments, it will follow that results obtained for different abnormalities and in different disorders by different methods may not be comparable and that modifications of the present cytogenetic methodology for bone marrow may lead to new findings of practical and theoretical significance.