Association of the tumour necrosis factor-α polymorphisms rs361525 and rs1800629 with susceptibility to psoriasis: a meta-analysis

Background. Evidence has suggested that tumour necrosis factor (TNF)-alpha may be involved in the aetiology of psoriasis, but the underlying association of the TNF-alpha polymorphisms -238G/A (rs361525) and -308G/A (rs1800629) with the risk of psoriasis is still unconfirmed. Aim. This meta-analysis was performed to determine whether the TNF-alpha -238G/A and -308G/A polymorphisms are associated with susceptibility to psoriasis. Methods. Eligible studies were identified by searching PubMed, EMBASE, CNKI (China National Knowledge Infrastructure), CBM (Chinese biomedical literature database) and WANFANG databases within a range of published years from 1990 to August 2012. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the different associations. Results. In total, 17 studies with 2847 cases and 2222 controls were found for -238G/A and 20 studies with 2975 cases and 2243 controls for -308G/A. The pooled results showed an overall increased risk of psoriasis for the -238G/A polymorphism (OR = 2.06, 95% CI = 1.45-2.94, P < 0.001 for AA/GA vs. GG) and a reduced psoriasis risk with the -308G/A polymorphism (OR = 0.68, 95% CI = 0.59-0.79, P < 0.001 for AA/GA vs. GG). This association was only present in early-onset psoriasis (OR = 3.68, 95% CI = 2.17-6.24, P < 0.001 for -238G/A; OR = 0.56, 95% CI = 0.43-0.72, P < 0.001 for -308G/A), whereas there was no association (OR = 0.98, 95% CI = 0.56-1.70, P = 0.92 for -238G/A) or a unreliable association (OR = 0.66, 95% CI = 0.46-0.94, P = 0.02 for -308G/A) in late-onset psoriasis. Conclusions. This meta-analysis suggests that the TNF-alpha -238 and -308 promoter polymorphisms may play different roles in conferring susceptibility to psoriasis. Functional and well-designed studies should be conducted to confirm these results.