Eosinophilia during fludarabine treatment of chronic lymphocytic leukemia

Although eosinophilia has been reported as a side effect of purine analogue s, there is no report on fludarabine-induced eosinophilia in chronic lympho cytic leukemia (CLL). During chemotherapy with fludarabine and cyclophospha mide, we observed two cases of significant eosinophilia. A 67-year-old pati ent with CLL developed bone marrow and peripheral blood eosinophilia up to 7.9 x 10(9)/l, the highest eosinophil count ever, reported during treatment with a purine analogue. The eosinophilia persisted for 33 days. Another pa tient developed bone marrow eosinophilia without eosinophilia in the periph eral blood. These are the first documented cases of fludarabine-induced eos inophilia in CLL, and this side effect may conceivably be more common than previously recognized.