RESUMO
BACKGROUND: A number of studies have suggested a bidirectional relationship of periodontitis with rheumatoid arthritis (RA) and type 2 diabetes mellitus (T2DM). However, the genetic factors that underlie these relationships have not been elucidated. METHODS: We conducted a multicenter case-control study that included 185 patients with RA and chronic periodontitis (CP), 149 patients with T2DM and CP, 251 patients with CP, and 130 systemically and periodontally healthy controls from a cohort of Japanese adults to assess the shared genetic risk factors for RA and CP as well as for T2DM and CP. A total of 17 candidate single nucleotide polymorphisms (SNPs) associated with RA, T2DM, and CP were genotyped. RESULTS: Multiple logistic regression analyses revealed that the KCNQ1 rs2237892 was significantly associated with comorbidity of RA and CP (P = 0.005) after adjustment for age, sex, and smoking status. The carriers of the T allele among patients with RA and CP showed significantly higher disease activity scores including 28 joints using C-reactive protein values than the non-carriers (P = 0.02), although the age, female percentage, and smoking status were comparable. Other SNPs were not associated with comorbidity of RA and CP, T2DM and CP, or susceptibility to CP. CONCLUSION: The results of the present pilot study suggest for the first time that the KCNQ1 rs2237892 may constitute a shared genetic risk factor for RA and CP, but not for T2DM and CP in Japanese adults.