Genetic variations in IL6 and IL12B decreasing the risk for psoriasis

Background: Psoriasis is a chronic inflammatory skin disorder. Recent studies associated a number of genetic variants to this immune-mediated pathology.

Objective: This study aims to assess whether the association between the non-susceptibility allelic variants of IL12B single-nucleotide polymorphism (SNPs) rs3212227 and rs6887695, IL23R SNPs rs11209026 and rs7530511, IL6 SNP rs1800795 and HLA-Cw6 could be correlated with decreased risk for psoriasis.

Material and methods: We genotyped 67 psoriasis patients and 69 healthy subjects for polymorphisms of IL12B rs3212227 and rs6887695, IL23R rs11209026 and rs7530511, IL6 rs1800795 and for the presence of HLA-Cw6. The patients and controls were recruited from Dermatology Department, part of "Tor Vergata" Clinic, Rome. Demographic data of the control group matched those of psoriasis patients, with a female:male ratio of 2.55 and mean age of 45.5±12.2 years for patients and 44.8±11.7 years for controls.

Results: The following genotypes were less frequent in patients: IL12B SNP rs6887695 CC (OR, 0.179; CI95% 0.046-0.699; p=0.01), IL6 SNP rs1800795 CG (OR, 0.367; CI95% 0.179-0.753; p=0.006) and IL6 SNP rs1800795 CC (OR, 0.069; CI95% 0.008-0.586; p=0.01). Also the HLA-Cw6 allele was rarely found in controls (OR, 0.459; CI95% 0.230-0.916; p=0.02). The multivariate analysis showed that the existence of at least one C allele in both IL12B SNP rs6887695 and IL6 SNP rs1800795 or the absence of HLA-Cw6 allele and at least one C allele in IL12B SNP rs6887695 or IL6 SNP rs1800795 is associated with a lower risk of psoriasis (OR, 0.185; CI95% 0.037-0.929; p=0.04). The presence of at least one C allele in both IL12B SNP rs6887695 and IL6 SNP rs1800795 and the absence of HLA-Cw6 allele decreased even further the risk of psoriasis (OR, 0.038; CI95% 0.006-0.244; p=0.001).

Conclusion: We report carriers of variations in the IL6, IL12B and absence of HLA-Cw6 as having decreased risk for psoriasis.