Atypical variant of hypereosinophilic syndrome responsive to imatinib mesylate: A case report

Abstract

16530 Background: Idiopathic hypereosinophilic syndrome (HES) was first described by Chusid et al in 1975. The diagnosis of HES rests on three features: A persistent eosinophil count of greater than >1500 cells/μL for more than 6 months, no other etiologies for eosinophilia, and symptoms of organ involvement. The requirement of end organ damage differentiates HES from benign eosinophilia, in which there is no organ damage, in spite of years of eosinophilia. Methods: We present a case of a 28-year-old African American male, admitted for shortness of breath and leg swelling. Past medical history was significant only for asthma. Results: Laboratory investigation demonstrated an average white blood cell count of 15,900 U/L and eosinophilia of 29.6% over a 6-month period. Stool studies for ova and parasite, Rheumatoid factor, antinuclear antibody, pANCA, cANCA and complements were within normal limits. Thyroid stimulating hormone, liver function studies, and erythrocyte sedimentation rate were within normal limits. IgE level was 158 (mildly high). Peripheral smear showed only mature eosinophils. A bone marrow biopsy showed a hypercellular marrow consistent with an atypical variant of HES. Cytogenetic studies did not reveal any clonal abnormalities. Trans-esophageal echocardiogram showed severe mitral regurgitation. During the hospital course the patient had a mitral valve replacement with a St. Jude’s mechanical valve and mitral valve pathology showed post inflammatory changes and ventricular myocardial biopsy staining for eosinophilic major basic protein confirmed eosinophilic changes. The patient remained refractory to aggressive steroid therapy, and was started on imatinib mesylate, which lead to a complete remission. Conclusions: HES is a very rare and often fatal condition. A 1989 French study showed a 5-year survival of 80%, and a 15-year survival of 42%. HES has three known variants: The atypical myeloproliferative variant of HES is often refractory to glucocorticosteroid therapy, but responds to treatment with the tyrosine kinase inhibitor, imatinib mesylate. No significant financial relationships to disclose.