Interleukin 1 beta promoter polymorphism is associated with keratoconus in a Japanese population

Purpose: Polymorphisms in the interleukin 1 alpha (IL1A) and IL1B gene regions were previously associated with keratoconus in a Korean population. In the present study, we investigated whether the IL1A and IL1B polymorphisms are associated with keratoconus in a Japanese population. Methods: A total of 169 Japanese patients with keratoconus and 390 Japanese healthy controls were recruited. We genotyped one IL1A single nucleotide polymorphism (SNP; rs2071376) and two IL1B SNPs (rs1143627 and rs16944) to compare the frequencies of alleles, genotypes, and haplotypes between cases and controls. Results: Statistically significant association was observed for rs1143627 (-31 T>C) in the IL1B promoter region; the T allele of rs1143627 was associated with an increased risk of keratoconus (p=0.014, corrected p value [pc]=0.043, odds ratio=1.38). The C allele of rs16944 (-511 C>T) in the IL1B promoter region had a 1.33-fold increased risk of keratoconus, although this increase did not reach statistical significance (p=0.033, pc=0.098). The TT genotype of rs1143627 was weakly associated with an increased risk of keratoconus (p=0.033, pc=0.099, odds ratio=1.52). However, no significant differences were found in the allele and genotype frequencies between the cases and controls for rs2071376 in IL1A. Regarding haplotypic diversity, the haplotype created by the T allele of rs1143627 and C allele of rs16944 was associated with a 1.72-fold increased risk of keratoconus (p=4.0×10^-5, pc=1.6×10^-4). Conclusions: Our results replicate associations reported recently in a Korean population. Thus, IL1B may play an important role in the development of keratoconus through genetic polymorphisms.