Chronic myeloid leukemia manifested during megakaryoblastic crisis.

We describe a 38-year-old man with a chronic myeloproliferative syndrome characterized by elevated white blood cell and platelet counts and increased blasts in the peripheral blood. Bone marrow aspiration was a "dry tap" and the biopsy specimen was hypercellular with numerous blasts, atypical megakaryocytes, and increased reticulin fibrosis. The blasts exhibited cytochemical reactivity for nonspecific esterase and PAS and immunohistochemically were positive for factor VIII, supporting megakaryoblastic lineage. Cytogenetic studies of peripheral blood revealed the t(9;22)(q34;q11). We interpreted these findings to be most consistent with chronic myeloid leukemia (CML) manifested at the time of megakaryoblastic crisis. Although the initial complete blood count showed leukocytosis and thrombocytosis, the patient subsequently had pancytopenia with clinical and pathologic findings consistent with acute myelofibrosis (AMF). Cytosine arabinoside and etoposide chemotherapy induced remission of the acute leukemia. We conclude that CML infrequently presents itself in megakaryoblastic crisis and that such cases may result in the clinicopathologic syndrome of AMF. The success of chemotherapy in this case also suggests that intensive antileukemic therapy may be useful in other patients with either CML-blast crisis or the clinicopathologic syndrome of AMF.