Peripheral neuropathy in hypereosinophilic syndrome.

We evaluated seven patients with the hypereosinophilic syndrome (HES) to define the clinicopathologic spectrum of the peripheral neuropathy. Clinically, three had evident polyneuropathy; the others were asymptomatic, although they had electrophysiologic evidence of neuropathy. Nerve conduction studies and EMG were compatible with axonal neuropathy. Morphometry of sural nerves from four patients ranged from normal to marked axonal loss, more prominent in large myelinated fibers. Demyelination was rare, and there was no evidence of vasculitis. Neuropathy may be produced by an eosinophil-derived neurotoxin.