Ph1 -positive CML associated with megakaryocytic hyperplasia and thrombocythemia and an abnormality of chromosome no. 3.

A patient with Philadelphia (Ph1) chromosome positive chronic myelocytic leukemia is described, who had in blast crisis in addition an abnormality of chromosome No. 3; ins(3; 3)(q26; q21q26). This abnormality might be connected with hyperplasia of megakaryocytes and thrombocythemia, as recently reported in patients with acute leukemia. In the initial phase of the disease our patient had also thrombocythemia, hyperplasia of megakaryocytes with morphological abnormalities. Furthermore, when blast cells were culture in diffusion chambers, differentiation into several cell lines occurred but not into megakaryopoiesis. It is, therefore, concluded that the involved band on chromosome No. 3 might contain the locus which controls megakaryocytic proliferation and platelet production but additional factors seem to be required for their expression.