[Atypical chronic myeloid leukemia with polymorphism of the BCR gene]

The region of greatest rupture of the gene BCR (M-bcr) was analysed with the restriction enzyme Bgl II plus a molecular probe containing the 5' end of M-bcr in a woman with atypical, Ph'-negative chronic myelogenous leukaemia. An abnormal DNA fragment of 5.0 kb and an extra band were found, suggesting rearrangement. Nevertheless, the use of several restriction enzymes and the addition of a different probe showed the existence of polymorphism with the enzyme Bgl II, which is an unusual finding. These findings stress the usefulness of using different restriction enzymes and molecular probes in the molecular study of chronic myelogenous leukaemia.