Hypereosinophilic syndrome: progression of peripheral neuropathy despite controlled eosinophil levels

Idiopathic hypereosinophilic syndrome (HES) is a disorder of the hematopoie tic system, characterized by persistent elevation in the total eosinophil c ount (> 1500/mu l)for over d months, associated with organ damage and no de tectable underlying cause. Treatment is centered on the reduction of total circulating eosinophils, which generally leads to remission of symptoms. We report a 68-year-old female patient with HES and peripheral neuropathy, pr esenting with cutaneous lesions, mental changes, cardiac and pulmonary symp toms, followed by right foot drop and eventually paraparesis, which caused an inability to ambulate. Weakness progressed to include the upper extremit ies despite adequate control of eosinophilia by steroids. Worsening of the peripheral neuropathy can occur despite lowering of the eosinophil levels.