In the past 15 years, 411 sporadic narcolepsy patients have been diagn
osed in the Hephata Klinik, Schwalmstadt, Germany. They were explored
for presence or absence of excessive daytime sleepiness and narcolepsy
in their relatives. A subset of 39 patients were explored for presenc
e or absence of parasomnias. Six patients had more than one relative a
ffected by narcolepsy-cataplexy. Forty-seven family members were inves
tigated with the Stanford Center for Narcolepsy Sleep Inventory and a
standardized parasomnia questionnaire. Twenty-four relatives had noctu
rnal polysomnographies and Multiple Sleep Latency Tests. HLA class I t
yping was performed in all sporadic and familial cases, class II and m
icrosatellite typing was performed in all members of multicase familie
s. Based on the Finnish prevalence study by Hublin et al., 1994, the r
elative risk for first degree relatives to develop narcolepsy-cataplex
y was in our sample 16.5, 34.2 for excessive daytime sleepiness and 42
6.9 for parasomnias. Cataplexy, excessive daytime sleepiness and singl
e narcoleptic symptoms in the multicase families segregate with the DR
B11501, CARII:200, CARI: 103, DQB1*0602 haplotype. In two families, m
embers with narcolepsy and isolated symptoms have inherited the DRB11
501/DQB10602 haplotype from the nonaffected parent. The observed segr
egations in these two families may support the view that narcoleptic s
ymptoms are expressed by DRB11501/DQB1*0602 carriers, independent of
haplotype origin. Parasomnias do not segregate with a specific haploty
pe. The frequency of parasomnias in narcolepsy is much higher than in
the general population. The empirical risk for first degree family mem
bers of narcolepsy patients to develop cataplexy seems to be low, wher
eas it is higher for EDS and highest for parasomnias.