Sweat gland duct cells in Lafora disease: diagnosis by skin biopsy.

Skin biopsies of three patients with Lafora disease (clinically typical and proven by liver biopsy) showed PAS-positive inclusions in numerous peripheral cells of eccrine sweat ducts. By electronmicroscopy, the inclusions consisted of polyglucosan-type material; they were not bounded by a membrane. Skin biopsy should be a convenient method of diagnosing Lafora disease.