Association of interleukin 1 receptor antagonist intron 2 variable number of tandem repeats polymorphism with vitiligo susceptibility in Gujarat population.

Background: Vitiligo is a multifactorial, polygenic, autoimmune skin disorder caused by selective destruction of melanocytes. Interleukin 1 receptor antagonist intron 2 polymorphism was found to be associated with various autoimmune disorders.

Aims: We aimed to investigate the association of interleukin 1 receptor antagonist intron 2 variable number of tandem repeats polymorphism (rs2234663) with vitiligo to assess interleukin 1 receptor antagonist transcript levels and to perform possible genotype-phenotype correlation.

Methods: Three hundred and seven vitiligo patients and 316 controls were enrolled in the study, genotyping of interleukin 1 receptor antagonist rs2234663 was performed by polymerase chain reaction, and relative gene expression of interleukin 1 receptor antagonist was carried out in peripheral blood mononuclear cells from patients (n = 36) and controls (n = 36) by real-time-PCR.

Results: A significant difference was observed in the frequency of interleukin 1 receptor antagonist *A (1/2) genotype among patients with active and stable vitiligo (P = 0.0172). Interleukin 1 receptor antagonist*A (2/2) genotype and allele frequencies were significantly different between SV patients and controls (P = 0.0246 and P = 0.0046, respectively). Significant difference was also observed for interleukin 1 receptor antagonist*A2 (allele) in active and stable vitiligo patients (P = 0.0060). However, other comparisons did not show any significant difference in genotype and allele frequencies. Moreover, interleukin 1 receptor antagonist*A (3/2) genotype was observed only in patients whereas interleukin 1 receptor antagonist*A (5/2) was observed only in controls. Gene expression analysis showed no significant difference in interleukin 1 receptor antagonist transcript levels in patients compared to controls (P = 0.5962). Interestingly, genotype-phenotype correlation analysis revealed that individuals with IL1RN*A (2/2) exhibited higher interleukin 1 receptor antagonist expression compared to other major genotypes interleukin 1 receptor antagonist*A (1/2) (P = 0.01) and interleukin 1 receptor antagonist*A (1/1) (P = 0.03).

Limitations: More case-control studies on interleukin 1 receptor antagonist rs2234663 polymorphism and gene expression from different ethnic populations are required to explore the impact of interleukin 1 receptor antagonist in vitiligo susceptibility.

Conclusion: Interleukin 1 receptor antagonist*A2 might be a risk factor for progressive vitiligo.