Published online Oct 16, 2016. doi: 10.12998/wjcc.v4.i10.328
Peer-review started: February 26, 2016
First decision: March 24, 2016
Revised: May 25, 2016
Accepted: June 27, 2016
Article in press: June 29, 2016
Published online: October 16, 2016
Idiopathic hypereosinophilic syndrome (HES) is a rare disorder characterized by peripheral eosinophilia exceeding 1500/mm3, a chronic course, absence of secondary causes, and signs and symptoms of eosinophil-mediated tissue injury. One of the best-characterized forms of HES is the one associated with FIP1L1-PDGFRA gene rearrangement, which was recently demonstrated as responsive to treatment with the small molecule kinase inhibitor drug, imatinib mesylate. Here, we describe the case of a 51-year-old male, whose symptoms satisfied the clinical criteria for HES with cutaneous and cardiac involvement and who also presented with vasculitic brain lesions and retroperitoneal bleeding. Molecular testing, including fluorescence in situ hybridization, of bone marrow and peripheral blood showed no evidence of PDGFR rearrangements. The patient was initially treated with high-dose steroid therapy and then with hydroxyurea, but proved unresponsive to both. Upon subsequent initiation of imatinib mesilate, the patient showed a dramatic improvement in eosinophil count and progressed rapidly through clinical recovery. Long-term follow-up confirmed the efficacy of treatment with low-dose imatinib and with no need of supplemental steroid treatment, notwithstanding the absence of PDGFR rearrangement.
Core tip: Imatinib mesilate is the mainstay therapy of hypereosinophilic syndrome (HES) associated with molecular rearrangement of the PDGFR gene. To date, HES has been associated with more than 50 different fusion genes resulting from various chromosomal and molecular abnormalities, highlighting the fundamental role of constitutively activated tyrosine kinases in the pathogenesis of this disease; however, few of these genes are routinely researched or detected in the clinical setting. We report a case of HES that showed no evidence of PDGFR rearrangement but responded quickly and effectively to the small molecule kinase inhibitor drug, imatinib mesilate.