A complex pattern of chromosome abnormalities in the acute phase of chronic granulocytic leukaemia.

The Philadelphia chromosome (Ph') is of particular interest because of its close association with chronic granulocytic leukaemia. Ph' is a distinct chromosome abnormality which is found in the marrow or blood cells of nearly all patients with this leukaemia, and appears to be generally specific to this or closely related disorders. Because of these features, Ph', unlike the chromosome abnormalities found in other tumours, has a strong claim to a close association with the aetiology of chronic granulocytic leukaemia, but a causal role has not been established. During the chronic phase of this leukaemia, Ph' is the only detectable chromosome change in the majority of cases, whereas in the acute terminal stages, Ph' is commonly associated with other chromosome abnormalities which vary considerably between patients. These secondary abnormalities resemble those found in acute leukaemia which is also characterized by a great variety of chromosome abnormalities, probably as a secondary development of the leukaemic state. Investigations of the transition from specificity to diversity of chromosome abnormality in chronic granulocytic leukaemia are of particular importance, because they might be expected to give some insight, not only into the relationship of chromosome abnormalities to tumour progression, but also into the nature of the specificity of the Ph' chromosome itself. The present paper reports a complex pattern of chromosome abnormalities in the bone-marrow cells of a 4I-year-old male patient, in the acute phase of the disease, who was a subject of earlier reports (Adams, Fitzgerald, and Gunz, I96I; Fitzgerald, Adams, and Gunz, i963). Detailed examination of the earlier material and of new material from this man revealed abnormalities of G group chromosomes additional to those reported previously, and also, that the abnormal sizes of the G chromosomes had caused Ph' to be overlooked in cells thought previously to be without it.