TNFSF4 and narcolepsy: Besides the HLA locus, several additional narcolepsy susceptibility loci were identified by genome-wide association studies [12–18], which suggest that immune-regulating genes (TCRA, P2RY11, TNFSF4, CTSH, TCRB, ZNF365, IL10RB-IFNAR1, and CCR1/CCR3) and a fatty acid metabolism-related gene (CPT1B/CHKB) are involved in the development of narcolepsy.