17 long arm isochromosome. A common anomaly in malignat blood disorders.

A cytogenetic anomaly consisting in the replacement of a 17 by its long arm isochromosome was identified as the only alteration in the marrow cells of two patients with acute granulocytic leukemia. In one case, the specific nature of the abnormal chromosome was established by newly available techniques. Since its identification in 1965, this structural anomaly, which implies 17 long arm duplication and short arm deletion, has been observed, as a sole or as an associated finding, in the malignant cells of a spectrum of blood disorders, including acute granulocytic leukemias, the blast crisis of chronic myeloid leukemia and lymphoreticular proliferative disorders. Attention is called to this particular rearrangement for its clinical as well as fundamental implications, as its presence in blood forming cells unfailingly hearalds a fast, fatal course of evolution.