Monozygotic twins concordant for the narcoleptic syndrome

Abstract

We report the first documented monozygotic twins who both had the narcoleptic syndrome. We assessed monozygosity by HLA antigens and by blood groups. In contrast to virtually all other narcoleptics, they had HLA-DQ1 instead of HLA-DR2; this helped to localize the gene, and perhaps explains its greater expressivity in these than in other twins.