Unilateral cataplexy associated with systemic lupus erythematosus

A patient with systemic lupus erythematosus (SLE) developed attacks of unilateral cataplexy precipitated by laughter. Unilateral cataplexy has not been described previously in detail and its association with SLE is unique. The clinical details, investigations, and diagnostic criteria are discussed and a causal relationship between cataplexy and SLE is suggested.