Effects of interleukin (IL)-6 gene polymorphisms on recurrent aphthous stomatitis

Recurrent aphthous stomatitis (RAS) is a common disease with oral ulceration in which cytokines are thought to play an important role. High levels of interleukin (IL)-6, a pro-inflammatory cytokine have been detected in the circulation of ulcer tissue. The purpose of the present study was to investigate if the IL-6 gene polymorphisms are associated with RAS or clinical characteristics of RAS in a cohort of Turkish population. 184 RAS patients and 150 healthy controls were included in the study. The genotypes of IL-6 gene −572G>C and −174G>C polymorphisms were determined using polymerase chain reaction based restriction fragment length polymorphism analysis. The genotype frequencies of −572G>C polymorphism showed statistically significant differences between RAS patients and controls (p = 0.01). Frequencies of GG + GC genotypes and G allele of −572G>C polymorphism were found higher in RAS patients (p = 0.0001, OR 10.8, 95 % CI 2.79–70.5; p = 0.0008, OR 2.06, 95 % CI 1.35–3.17, respectively). The genotype frequencies of −174G>C polymorphism also showed statistically significant differences between RAS patients and controls (p < 0.0001). Frequencies of GG genotype and G allele of −174G>C polymorphism were found higher in RAS patients (p < 0.0001, OR 4.87, 95 % CI 3.06–7.85; p < 0.0001, OR 3.82, 95 % CI 2.64–5.59, respectively). GG–GG combined genotype and G–G haplotype of −174G>C to −572G>C loci were also significantly higher in RAS patients (p < 0.0001 and p = 1.5 × 10⁻⁸, respectively). After stratifying clinical and demographical characteristics of RAS patients according to IL-6 gene polymorphisms, an association was observed between family history of RAS and −174G>C polymorphism (p = 0.011). Susceptibility effects of both IL-6 gene −572G>C and −174G>C polymorphisms for RAS were observed. Further studies are necessary to prove the association of IL-6 gene polymorphisms with RAS.