Serum cytokine levels in Kleine–Levin syndrome

•Kleine–Levin Syndrome (KLS) is a rare episodic sleep disorder.•The pathogenesis of Kleine–Levin Syndrome is unknown but could involve the immune system.•Serum was collected from 52 people with KLS, 28 of which were taken during an episode.•The levels of 51 cytokines and chemokines were overall similar in serum collected in and out of an episode.

ObjectiveKleine–Levin Syndrome (KLS) is a rare sleep disorder causing recurrent symptomatic episodes of severe hypersomnia, cognitive impairment, apathy, and derealization. These episodes are interspersed with long periods of normal sleep, cognition, and behavior. The pathogenesis of KLS is still unknown. The objective of this study was to determine serum cytokine levels in patients with KLS during and between episodes.Patients/MethodsFifty-two typical KLS patients were included in the study of whom 17 patients donated blood samples both during and between episodes. Blood samples were collected in USA, France, and Taiwan in a clinical setting. Processing of the samples was performed at the Stanford Center for Sleep Sciences and Medicine.ResultsWe did not observe any changes in serum cytokine levels during KLS episodes compared to between episodes. In a small cohort of asymptomatic KLS patients and age- and gender matched healthy controls (n = 8/group) whose blood samples were all collected and processed at the same day; asymptomatic KLS patients had significantly higher levels of serum sVCAM1 cytokine compared to healthy controls.ConclusionThese data suggest that KLS episodes are not accompanied by an abnormal systemic immune reaction.