Diversity of clinical manifestations and response to corticosteroids for idiopathic hypereosinophilic syndrome: retrospective study in 33 patients.

Idiopathic hypereosinophilic syndrome (IHES) is characterized by blood hypereosinophilia with no underlying cause and eosinophilia-associated organ dysfunction. Thirty-three patients, 20 female (61%) and 13 male (29%), with a median age of 56 years at diagnosis (range 16-77 years) were included in the study. The median blood eosinophilia at diagnosis was 7.6 × 10(9)/L and the median percentage of eosinophils in the bone marrow was 39.5%. The most common clinical manifestations were splenomegaly and cardiac involvement. Corticosteroids (CS) as monotherapy were initiated in all study patients. The median starting dose of prednisone was 30 mg daily (range 5-85 mg), and the maintenance dose varied from 5 mg twice weekly to 60 mg daily. Overall, 21 patients (64%) responded to CS within a week. Seven patients (21%) were resistant or intolerant to CS. Five patients (15%) achieved a 50% reduction of blood eosinophilia. In conclusion, CS were found to be highly effective in IHES with manageable side effects.