We report on an 11-year-old girl, presenting with clinical features suggesting both pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) and Kleine-Levin syndrome (KLS), who was successfully treated with penicillin prophylaxis. KLS is a sleep disorder characterized by recurrent episodes of hypersomnia and at least one of the following symptoms: (1) cognitive or mood disturbances, (2) megaphagia with compulsive eating: (3) hypersexuality with inappropriate behaviors: and (4) abnormal behavior. The etiopathogenesis is still unclear and there is no effective treatment other than symptomatic therapies. This intriguing case report suggests novel insight into the pathogenesis of this rare and enigmatic syndrome. (C) 2011 Elsevier B.V. All rights reserved.