Neuropathy in the hypereosinophilic syndrome.

Peripheral nerve dysfunction was a prominent clinical feature in each of three patients with the hypereosinophilic syndrome (HES). The neuropathy, occurring at the onset of marked eosinophilia or at a time of its worsening, had a painful onset, evolved over 1-4 weeks, and affected both sensory and motor function. Electrodiagnostic studies demonstrated both multifocal and generalized nerve involvement, with the former predominating (multiple mononeuropathy). Nerve and muscle biopsies from two patients revealed severe axonal degeneration with neurogenic atrophy of muscle. The eosinophilia decreased dramatically with corticosteroid treatment and the neuropathy gradually improved, but all three patients manifested residual neurologic disability 17-22 months after onset. The neuropathy may be on an ischemic basis or may be related to neurotoxicity of eosinophil products.