Familial narcolepsy in Finland.

Five patients with narcolepsy-cataplexy (aged 31-69, mean age at onset 15 years) and their 47 relatives were examined. They were interviewed in detail, all patients and 16 relatives (including all symptomatic cases) were examined neurologically and a multiple sleep latency test and HLA-typing were done. One case of narcolepsy and two cases of idiopathic hypersomnia were identified. All the other 45 relatives were symptom-free. The observed rate of familial cases (1/5 for narcolepsy and 2/5 for idiopathic hypersomnia) corresponds the results of other recent studies.