ERAP1 and narcolepsy: Narcolepsy, with and without cataplexy, was associated with HLA-DQB1*06:02,12 and the severity of narcolepsy without cataplexy was higher in HLA-DQB1*06:02-positive patients than in HLA-DQB1*06:02-negative patients.12,13HLA-B*51 was strongly associated with risk factors for Behçet’s disease,14 and a significant association between one SNP in the ERAP1 locus was observed only in HLA-B*51-positive patients.14 Hence there is a possibility that the genetic backgrounds might differ in PD subjects with or without HLA-DRB1*13:02.