[CD25 positive chronic eosinophilic leukemia with myelofibrosis].

A 70-year-old man was referred to our hospital in March 2001 for the purpose of evaluation for anemia and thrombocytopenia. Physical examination revealed hepatosplenomegaly, normal skin, and normal neurologic findings. Blood examination showed a white blood cell count of 10,900/microliter, with a differential count of 58.5% eosinophils and 3.5% blast cells. Flow cytometric analysis of eosinophils revealed that they were positive for CD33, CD13, CD25, and HLA-DR. Bone marrow aspiration could not be performed due to dry tap, and bone marrow core biopsy specimen revealed severe myelofibrosis with blastoid cells proliferation. Cytogenetic analysis of bone marrow cells showed isochromosome 17. FISH analysis using a RAR alpha probe (17q21.1) demonstrated 62% of peripheral blood nucleated cells having three signals. BCR/ABL gene rearrangement by FISH analysis was not observed. Allergic disease, infectious disease, parasitic disease, collagen vascular diseases, pulmonary disease, and neoplastic disorders were excluded. Therefore, a diagnosis of chronic eosinophilic leukemia was made. The patient had no symptoms of hypereosinophilia. However, eosinophils with sparse granulation, positivity for CD25, elevated serum levels of soluble IL-2 receptor, and elevated serum levels of eosinophil cationic protein suggested activation of eosinophils. Further analysis is needed regarding the activation of eosinophils in chronic eosinophilic leukemia.