Association of TNF‐α polymorphisms with adult dermatomyositis and systemic lupus erythematosus in Bulgarian patients

Background Single‐nucleotide polymorphisms (SNPs) of tumor necrosis factor‐alpha (TNF‐α) have been implicated in various autoimmune diseases; however, the results are quite controversial, and there is still no widely accepted opinion about their role in the pathology of the autoimmune diseases. This is a pilot study to investigate the association of six SNPs of the TNF‐α gene with the risk of adult dermatomyositis (DM) and systemic lupus erythematosus (SLE) in Bulgarian patients. Materials and methods Twenty‐seven patients with DM and 27 with SLE were included in this study. Genomic DNA was extracted from the peripheral blood, and six SNPs (?1031T/C, ?863C/A, ?857C/T, ?308G/A, ?238G/A, +489G/A) were selected for investigation by polymerase chain reaction‐restriction fragment length polymorphism analysis. Results We found association between the TNF‐α?1031CC genotype and SLE (P = 0.025) and tendency for association with DM (P = 0.0876). The association appeared even stronger in the female patients with SLE (P = 0.024) and DM (P = 0.067). The TNF‐α?857GG genotype shows weak association with SLE (P = 0.097, OR 2.06, 95% CI 0.81–5.29) when analyzed for the whole group, but it appeared significantly associated with SLE in women (P = 0.048, OR 3.23, 95% CI 0.93–11.14). The ?863C allele showed association with arthritis in patients with SLE (P = 0.008). The haplotype analysis revealed a significant association between TNF ?1031C/?863C/?857C/?308G/+489G haplotype with both DM (P = 0.022) and SLE (P = 0.007) in women. Conclusions The TNF‐α polymorphisms are associated with increased relative risk mainly for SLE, particularly in women, while their role for DM is less evident and needs further analysis in an enlarged sample cohort.