Excellent response to interferon therapy in a patient with hypereosinophilic syndrome and elevated serum immunoglobulin E levels.

The hypereosinophilic syndrome (HES) is a heterogeneous disease characterized by sustained eosinophilia for a period of at least six months with evidence of organ involvement. Its manifestations range from a benign disorder not requiring any therapy to an aggressive, malignant variety refractory to common treatments. Diverse therapies have been used, including steroids, hydroxyurea, and chemotherapy, with variable responses. Recently alpha-interferon therapy has been shown effective in this disorder. Of the various prognostic factors, elevated serum immunoglobulin E (IgE) levels is considered among the most favorable, with most patients presenting with a "benign" disorder, not requiring therapy. We describe a patient presenting with an aggressive variant of HES despite having elevated IgE levels. The patient had a dramatic and lasting response to alpha-interferon.