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.