Postmortem studies on narcoleptic patients affirm the loss of cells producing this neuropeptide in the lateral hypothalamus (∼50,000 to 100,000 cells).7, 8A higher prevalence of the HLA-DQB1*0602 allele and a low hypocretin concentration in the central nervous system characterize individuals with narcolepsy and cataplexy. This evidence concerns the gene HCRT and narcolepsy.