Blastic crisis in previously clinically silent chronic myelogenous leukemia.

A patient is described in whom CML first presented as blastic crisis. The diagnosis of CML was based upon the findings of Ph(1) chromosome in the bone marrow, basophilia in the peripheral blood, absence of NAP activity in the leukocytes, elevated serum vitamin B(12) and an enlarged firm spleen. CML with blastic crisis as its first expression is relatively rare, as compared to CML in which blastic crisis appears as a phase of prolonged clinically manifest disease.