Meta-analysis of vitamin D receptor polymorphisms and psoriasis risk

Background Vitamin D receptor (VDR) gene polymorphisms have been studied as candidate variants that affect psoriasis risk. However, results have been conflicting. Methods We reviewed studies on VDR polymorphisms and psoriasis risk published to October 1, 2011, and quantitatively summarized associations of the most widely studied variants (FokI, TaqI, ApaI, BsmI) using meta-analysis. Associations were measured using random-effect odds ratios (ORs) combined with 95% confidence intervals (CIs). Results Eleven eligible studies, encompassing 1106 cases and 1209 controls, were retrieved from electronic databases and included in this review. The results were heterogeneous, which may be partly explained by small sample bias, the phenomenon of winner's curse, and differences among populations. For FokI and ApaI polymorphisms, we did not find any evidence of association. A borderline allelic association was found for the BsmI B variant after exclusion of the earliest significant report (OR=0.81, 95% CI 0.680.98; P=0.04, inconsistency index [I2]=12.7%). Among Caucasian subjects, the TaqI t allele was nominally associated with psoriasis risk (OR=0.77, 95% CI 0.640.97; P=0.012, I2=0), with homozygous carriers (tt vs. TT, OR=0.59, 95% CI 0.390.90; P=0.01, I2=0) and recessive model (tt vs. Tt+TT, OR=0.66, 95% CI 0.440.98; P=0.04, I2=0) as protective factors. None of these associations persisted after adjustment for multiple comparisons. No publication bias was detected in this meta-analysis. Conclusions No genetic variant examined in the VDR gene showed a robust and reproducible association with risk for psoriasis. Any association that may exist is likely to be weak and potentially restricted to specific populations.