Lambert-Eaton myasthenic syndrome associated with Sjögren's syndrome and discoid lupus erythematosus.

A 65-year-old woman with facial erythema and hypergammaglobulinemia developed excessive fatigability. A diagnosis of Lambert-Eaton myasthenic syndrome (LEMS) was made from electrophysiological studies. She had symptoms and laboratory data compatible with probable Sjögren's syndrome. Skin biopsy revealed the histological findings of discoid lupus erythematosus. Treatment with 3,4-diaminopyridine resulted in the improvement of fatigability. LEMS should be recognized as a treatable complication of systemic autoimmune diseases.