Kleine-Levin syndrome and bipolar disorder: a differential diagnosis of recurrent and resistant depression.

International audienceOBJECTIVES: Kleine-Levin syndrome (KLS) is a rare sleep disorder (1-2 reported cases per one million individuals) primarily affecting young subjects. Episodes are characterized by hypersomnia, cognitive impairment, feelings of derealization, and, less frequently, hyperphagia (66%), hypersexuality [53% (principally men)], and depressed mood [53% (predominantly women)]. KLS cases are frequently misdiagnosed and pose therapeutic challenges (i.e., amantadine and mood stabilizers are only marginally effective). The cause of KLS is unknown, but an association between KLS and mood disorders has been suggested by some clinical analogies. METHODS: We report the case of a 44-year-old Caucasian woman with bipolar I disorder referred by her psychiatrist to our psychiatric center for recurrent and resistant major depression according to DSM-IV-TR criteria. RESULTS: Following examination, we confirmed the diagnoses of bipolar I disorder and KLS. The patient experienced about 15 evenly distributed KLS episodes, each lasting about one week, which occurred during the six years following her first manifestation at age 18 years. An electroencephalogram was performed during a KLS episode and showed high-amplitude theta waves in the left and right temporal lobes, with predominance in the left hemisphere. The pronounced bipolar disorder symptomatology, starting at 15 years of age with major depression and a suicide attempt, had impeded the identification of KLS, which was not diagnosed until the age of 42. CONCLUSIONS: Bipolar disorder may obscure KLS, with each condition adversely affecting the course of the other, and consequently, the co-occurrence of KLS and bipolar disorder may be underestimated. KLS and bipolar disorder may share common vulnerability factors, such as immune-inflammatory and circadian disturbances, and there may be a genetic predisposition for both. Additionally, mood stabilizers may be effective for KLS and bipolar disorder