[Chronic myelogenous leukemia with marked thrombocytosis]

We report a case of chronic myelogenous leukemia (CML) with marked thrombocytosis. The patient was a 68-year-old woman who showed marked thrombocytosis (> 200 x 10(4)/microliter), a slightly increased leukocyte count without any immature myeloid cells in the peripheral blood, and no hepatosplenomegaly. Philadelphia chromosome (Ph) was detected by karyotype analysis and FISH. The bcr-abl transcript was detected by RT-PCR and the break point was located in the major bcr. Treatment with interferon-alpha was effective, reducing the proportion of Ph-positive cells from 56% to 7% within 21 months. Detailed study of atypical cases of CML such as the present one may provide additional information about the disease pathogenesis.