Development of hairy cell leukemia in a patient treated with cytoreductive agents for essential thrombocythemia.

The association of second malignancies in hairy cell leukemia (HCL) is well recognized. Most of these malignancies are either solid tumors or lymphoproliferative disorders rather than myeloproliferative disorders. But these malignancies are usually related to a complication of the drug treatment for HCL. The chronological sequence of HCL occurring after a hematological disorder is very rarely described. This report describes the first case, to our knowledge, of a patient who developed HCL five years after essential thrombocythemia that was treated with oral cytoreductive agents. Pathogenesis of the coexistence of both diseases is discussed.