Recurrent subacute encephalopathy as part of an idiopathic hypereosinophilic syndrome

History: An 81-year-old man, impreviously good health, suddenly developed c onfusion and rapidly progressive severe tetraparesis. Investigations: Peripheral blood and bone marrow revealed marked eosinophil ia: allergic. parasitic, neoplastic or vasculitic causes were excluded. Mag netic resonance imaging demonstrated multiple lesions in the cortical and s ubcortical white matter. Diagnosis, treatment and course: The findings indicated idiopathic hypereos inophilic syndrome involving the central nervous system and treatment with high doses of glucocorticoids was started. After a stormy course almost com plete recovery occurred. Conclusion: Idiopathic hypereosinophilic syndrome can rarely manifest itself a an isolated severe subacute encephalopathy.