Paediatric-onset psoriasis is associated with ERAP1 and IL23R loci, LCE3C_LCE3B deletion and HLA-C*06

Recent genome-wide association studies have identified several genetic risk factors for psoriasis, but data on their association with age at onset are lacking.To compare the association between known risk alleles and psoriasis in well-defined cohorts with paediatric- and adult-onset psoriasis.Based on previous studies we selected seven genes and loci associated with psoriasis. Patients with paediatric-onset (18 years) and adult-onset psoriasis (≥ 18 years) and controls were genotyped. Genotype frequencies were compared between controls (n = 450) and all cases (n = 217), and between controls and cases stratified for confirmed age at onset (paediatric onset n = 80, adult onset n = 85).Paediatric-onset psoriasis showed a significant association with single nucleotide polymorphisms in the ERAP1 (P = 0.042) and IL23R loci (P = 0.042), LCE3C_LCE3B-del (P = 0.003) and HLA-C*06 (P = 1.72 × 10(-19)) when compared with the control group. A significant association of these four genes was also demonstrated when all psoriasis cases were compared with controls. In adult-onset psoriasis a significant association was found for HLA-C*06 (P = 5.11 × 10(-6)) and for LCE3C_LCE3B-del (P = 0.042). No associations were found for the IFIH1, IL12B and TRAF3IP2 loci.Notwithstanding the small cohort sizes, we demonstrated an association with established and recently discovered genetic risk factors in paediatric-onset psoriasis including genes involved in epidermal barrier function and adaptive immunity. Our data suggest that heritable factors may play a more important role in paediatric-onset psoriasis than in adult-onset psoriasis.