HLA-DR2 association with excessive somnolence in narcolepsy does not generalize to sleep apnea and is not accompanied by systemic autoimmune abnormalities.

Recent reports that nearly all patients with narcolepsy have the HLA-DR2 phenotype suggest that autoimmunity may underly the etiology or pathogenesis of this disorder. Of 11 narcoleptic patients in the present study, 9 were HLA-DR2, confirming the strong association with this class II antigen but indicating that this is not an obligatory phenotype. In contrast only 3/10 patients with sleep apnea were HLA-DR2, suggesting that this form of excessive somnolence has a different etiopathogenesis. Significant levels of rheumatoid factor, antinuclear antibodies or autoantibodies to native DNA, denatured DNA, histones, Sjogren's syndrome B antigen, or Smith antigen were undetectable in sera from narcoleptic patients. Antibodies to rodent brain, primate brain stem, and neurocytotoxic antibodies were also not found. These results along with the absence of laboratory signs and clinical features of a systemic inflammatory process indicate that if narcolepsy is an autoimmune disease, the underlying lesion or pathologic condition may be confined to the central nervous system.