A diagnostically difficult case of chronic myeloid neoplasm with eosinophilia and abnormalities of PDGFRA effectively treated with imatinib in accelerated phase

Chronic myeloid neoplasm with eosinophilia and abnormalities of platelet‑derived growth factor receptor α (PDGFRA), referred to until 2008 as chronic eosinophilic leukemia, is distinguished from hypereosinophilic syndrome (HES), if accompanied by genetic abnormalities that enable to determine eosinophil clonality. Typically, HES has a benign course and glucocorticosteroids suffice to achieve remission. In chronic myeloid neoplasm with eosinophilia and abnormalities of PDGFRA the FIP1L1‑PDGFRA fusion gene can be detected. Its product is a protein showing tyrosine kinase activity leading to malignant proliferation of eosinophil precursors. Differential diagnosis of HES is often difficult because hypereosinophilia may also be reactive and may occur in many nonhematological as well as hematological disorders. Thus, reverse‑transcription polymerase chain reaction (RT‑PCR)is indicated in all patients with HES in order to detect the FIP1L1‑PDGFRA transcript. Traditional treatment of chronic myeloid neoplasm with cytostatic drugs results in a short‑term and transient remission or stabilization of the disease. We present the case of a 52‑year‑old patient with chronic myeloid neoplasm with eosinophilia and abnormalities of PDGFRA, in whom acceleration occurred after a year of cytostatic therapy with hydroxyurea and was successfully treated with imatinib. It was impossible to unequivocally determine the type of bone marrow disease based on histologic criteria, and a wide spectrum of molecular tests differentiating the type of myeloid proliferation were necessary to establish the diagnosis. RT‑PCR did not reveal BCR‑ABL or JAK2 V617F mutation. Further molecular testing showed rearrangement involving the FIP1L1 gene, thus enabling implementation of targeted therapy.