A case of myeloid neoplasm associated with eosinophilia and KIAA1509-PDGFRβ responsive to combination treatment with imatinib mesylate and prednisolone

A 41-year-old woman presented with dyspnoea, persistent leucocytosis and eosinophilia for 8 months. High-resolution computed tomography scan and pathology of bronchoalveolar lavage confirmed the diagnosis of hypereosinophilic pneumonitis. The patient was treated with prednisolone (0.5-1 mg/kg/day) for more than 20 weeks under the impression of hypereosinophilic syndrome, but without improvement of leucocytosis and eosinophilia. The bone marrow aspiration smear disclosed hypercellular marrow with myeloid hyperplasia and eosinophilia. The fusion gene detection was positive for KIAA1509-PDGFR beta. Myeloid neoplasm associated with eosinophilia and abnormality of PDGFR beta was then diagnosed (Tefferi A, Vardiman JW, Leukemia, 22, 2008, 14). The tyrosine kinase inhibitor, imatinib mesylate (Glivec; 200 mg/day), was administered along with prednisolone (0.25-1 mg/kg/day). White blood cell (WBC) count decreased from 49 500/mu L to 17 200/mu L, and eosinophil count decreased from 1932/mu L to 35/mu L, which represent percentage dropped from 7.7%> to 0.2%. Withdrawal of prednisolone was done to avoid adverse events. However, absolute eosinophil count increased progressively despite the continue administration of imatinib and negative detection PDGFR beta fusion gene. The patient then received combination therapy of imatinib and prednisolone again. WBC and absolute eosinophil were normalized subsequently. We had discontinued the prednisolone one more time, and rebound of eosinophilia was seen again. The phenomenon of rebounding of eosinophilia was observed in two subsequent withdrawals of prednisolone. Either steroid or imatinib mesylate alone failed to achieve complete haematological response. A synergistic effect of imatinib and steroid is postulated.