Chronic Eosinophilic Leukemias and the Myeloproliferative Variant of the Hypereosinophilic Syndrome

Among patients with hypereosinophilia, a myeloproliferative variant is recognized. In many of these patients a diagnosis of eosinophilic leukemia can be made. The molecular mechanism is often a fusion gene, incorporating part of PDGFRA or PDGFRB, encoding anaberrant tyrosine kinase. Prompt diagnosis of such cases is important since specific tyrosine kinase inhibitor therapy is indicated.