[Idiopathic hypereosinophilic syndrome in a child with fever and hepatomegaly].

Idiopathic hypereosinophilic syndrome (IHES) in children is a rare disorder. A 1-year-old girl presented to our hospital for evaluation of eosinophilia. At the onset, her white blood cell count in peripheral blood was 70,600/μl with 74% eosinophils. She had a high fever and mild hepatomegaly but had no remarkable evidence of organ involvement by CT, MRI and ultrasonography. She was diagnosed with IHES without any evidence of secondary eosinophilia, expression of the FIP1L1-PDGFRα fusion transcript, chromosomal abnormalities, and aberrant T-cell populations. The serum IgE, vitamin B12, IL-5 and TARC levels were normal. Systemic administration of corticosteroid and suplatast tosilate resolved the symptoms promptly and resulted in improvement of eosinophilia.