Abstract
Kliene Levin syndrome (KLS) is a peculiar sleep disorder of youth, consisting of idiopathic periodic hypersomnia attacks associated with behavioral and sometimes psychiatric symptoms during an attack. With the growing awareness of the syndrome and a steep rise in published cases, it became evident that psychiatric abnormalities may be present before the onset of hypersomnic events, in between events and first appear following years after complete recovery. Those observations suggest that psychiatric morbidity may be part of the symptomatology of KLS. In the present paper the results of a systematic literature search of publications using the key words KLS with psychiatric features, Atypical KLS, KLS like, KLS mimic and sleeping beauty syndrome will be discussed, in attempt to support the view that KLS is indeed a neuropsychiatric disorder and not just a sleep disorder of youth. Moreover, the recognition that KLS might imitate psychosis and other psychiatric disorders in which periodic hypersomnia is present, may decrease the number of KLS patients in whom the correct diagnosis may be delayed or totally missed.