Hypersomnia in dystrophia myotonica: a neurophysiological and immunogenetic study.

Ten patients with dystrophia myotonica (8 adults and 2 prepubertal children), from three unrelated families, were investigated for diurnal sleepiness, using a sleep questionnaire and multiple sleep latency test (MSLT). Immunogenetic study was also carried out to assess the involvement of HLA region genes in modulating susceptibility to excessive diurnal sleepiness (EDS). EDS was reported by 5 patients and confirmed in each case by MSLT. In the whole patients group, mean daytime sleep latency was significantly shorter than in healthy controls matched for age and sex. At clinical or neurophysiological evaluation, EDS did not show the features associated with the narcoleptic type. In only one case hypersomnolence could be explained by underlying sleep-disordered breathing. HLA patterns were different from those frequently observed in the narcoleptic or non-narcoleptic types of hypersomnia. In patients with EDS, the frequency of the DQW1 and particularly of the DRW6-DQW1 haplotype appeared to be over-represented.