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Familial patterns of narcolepsy were investigated in a clinic population of 334 unrelated narcoleptic patients.40%of probands had at least 1 family member with an isolated daytime sleepiness complaint and 6%had a positive family history of narcolepsy.Multicase families were rare;only two families were found with 3 or more affected relatives.Family members often shared the same HLA-DR2 haplotype as the proband but did not have narcolepsy.However,the risk of disease for first-degree relatives was six to eighteen times greater than that for unrelated individuals.Although most patients were HLA-DR2+,2 new HLA-DR2-individuals were found.The data predict that as many as 9%of unrelated North-American white patients with narcolepsy will be DR2-.Analysis of these and other data indicates that although strongly associated with disease,the HLA-DR2 haplotype is neither sufficient nor necessary for the development of narcolepsy. |
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