Kleine-Levin syndrome (KLS) is a rare disease of unknown etiology, the diagnosis of which can be challenging. We aimed to estimate KLS prevalence in French-speaking Switzerland, and assess differences with mimicking conditions.
In this cross-sectional study, KLS patients were identified through a population-based approach, including at our hospital and contacting all sleep-certified facilities and neurologists in French-speaking Switzerland. Furthermore, we identified patients referred to our center for suspected KLS that received other diagnoses. Relevant clinical data of these two groups was compared.
We identified 7 patients with diagnosed KLS (6 since 2009), leading to a prevalence estimation of 3.19 per million (95% confidence interval: 1.55-6.59). Median age at diagnosis was 17 years (range: 12-19), 71.4% of them were men, and mean diagnosis delay after the first episode was 20.1 ± 10.9 months. We identified 9 mimic patients referred to our center; they differed from KLS patients by their higher age at disease onset (median: 15 [range: 12-16] vs. 19 [range: 16-64] years; p < 0.001), suspected KLS as referral reason (more frequent in mimics, p = 0.003), and the presence of precipitating factors (more frequent in KLS, p = 0.011). Among the mimic patients, 77% (versus 28% in KLS) had a psychiatric diagnosis.
This study suggests a relatively higher KLS prevalence than previously reported. As compared to KLS, mimic patients have higher age at symptom onset, are more often initially referred for KLS suspicion, and have a higher prevalence of psychiatric disorders.