Tumor necrosis factor alpha gene promoter -238G/A polymorphism increases the risk of psoriasis vulgaris in Indian patients.

BACKGROUND: Tumor necrosis factor alpha (TNFα) gene -238G/A polymorphism (rs361525) is associated with psoriasis in several populations worldwide. To the best of our knowledge, there is no information about this polymorphism in Indian psoriatic patients. This study was undertaken to fill the gap in knowledge.

METHODS: This case-control study involved 72 patients with psoriasis vulgaris (PsV) and 72 age and gender matched healthy individuals. TNFα -238G/A polymorphism was genotyped by PCR-RFLP method.

RESULTS: TNFα -238A allele was 5 times commoner in PsV patients than in the control group (P = 4.1 × 10(-7) ; odds ratio [OR] = 6.5 [0.95 CI: 2.9-14.6]). Distribution of the genotypes in the two groups showed statistically significant difference in dominant genetic model (P = 2.3 × 10(-7) ) and not in recessive genetic model (P = 2.5 × 10(-1) ). Odds ratio for the occurrence of -238A genotype in PsV patients was 8.8 (0.95 CI: 3.5-20.2). The association showed no major difference when PsV patients were subgrouped into type I and type II categories and tested separately. Subgroup analysis on the basis of disease severity showed higher association with the moderate-severe subgroup (P = 2.4 × 10(-9) , OR 15.4 [0.95 CI: 5.8-41.0]) than with mild subgroup (P = 1.3 × 10(-2) , OR 3.8 [0.95 CI: 1.3-10.9]).

CONCLUSIONS: Our results indicate that TNFα gene -238G/A polymorphism increases the risk of developing psoriasis vulgaris among Indians. Also, the data show that severity and not the type affects the strength of association in this population.