A case of idiopathic hypereosinophilic syndrome with leptomeningeal dissemination and intraventricular mass lesion: an autopsy report.

A 43-year-old female presented with idiopathic hypereosinophilic syndrome (HES) manifesting as an intraventricular mass lesion and leptomeningeal and cerebral parenchymal infiltration by eosinophils, lymphocytes and macrophages. She had no history of either malignancy or allergic disorder. She complained of hearing disturbance caused by eosinophilic otitis media. Eosinophilia was detected in the peripheral blood. Hearing disturbance and eosinophilia improved with corticosteroid treatment. Six months later, she was admitted with disturbances of consciousness. Magnetic resonance imaging revealed a mass lesion in the right lateral ventricle and leptomeningeal involvement around the brain stem. Her symptoms deteriorated rapidly, and she died of brain stem malfunction. Autopsy demonstrated significant infiltration by eosinophils and lymphocytes into the mass lesion in the ventricle, subarachnoid space, perivascular space and parenchyma of the medulla oblongata. Histological examination of the bone marrow and other organs did not detect any evidence of parasites, malignancies, or systemic disorders in any organ. The final diagnosis was idiopathic HES. The present case shows that leptomeningeal dissemination and infiltration by eosinophils into the cerebral ventricles and brain stem should be considered in the course of idiopathic HES.