Interaction of MTHFR gene with smoking and alcohol use and haplotype combination susceptibility to psoriasis in Chinese population

To investigate the association of MTHFR gene polymorphism and additional gene–gene interaction with psoriasis risk. GMDR model was used to screen the best gene–smoking and gene–drinking interaction combinations. Logistic regression was performed to investigate association between two SNPs and psoriasis. For psoriasis patient-control haplotype analyses, the SHEsis online haplotype analysis software (http://​analysis.​bio-x.​cn) was employed. We found that carriers of homozygous mutant of rs1801133 polymorphism and heterozygous of rs1801131 are associated with increased psoriasis risk than those with wild-type homozygotes, OR (95%CI) were 2.01 (1.48–2.79), and 2.08 (1.56–2.86), respectively. We also found a significant gene–environment interaction between C677T and alcohol drinking. In all samples, the haplotype 1298A-677C was observed most frequently in two groups, with 49.43 and 55.71% for the patients and controls, respectively. The results also indicated that the haplotype containing 1298C and 677T alleles were associated with a statistically increased psoriasis risk, OR (95%CI) = 1.73 (1.12–2.46), P = 0.0002. Our study found that rs1801133, rs1801131 within MTHFR gene, and interaction between C677T and alcohol drinking and haplotype containing the 1298C and 677T alleles were all associated with increased psoriasis risk.