The influence of a TNF gene polymorphism on the severity of rheumatoid arthritis in the Brazilian Amazon

PurposeThe aim of this study was to investigate the influence of the TNF -308 G/A polymorphism in the promoter region of the tumor necrosis factor-α gene on the susceptibility and severity of rheumatoid arthritis (RA) in individuals from the Brazilian Amazon.MethodsA total of 323 individuals—192 healthy controls without arthritis and 131 individuals suffering from arthritis—were genotyped for this polymorphism using a methodology based on PCR-RFLP.ResultsThe frequency of the A allele (TNF2) in rheumatoid arthritis sufferers was not significantly higher than in the controls (p = 0.926; OR = 0.97; confidence interval 0.54–1.76). However, using a logistic regression model, when the patients were stratified according to whether the manifestations were preponderantly articular or systemic, there was a strong association between the TNF2 allele and systemic arthritis (p = 0.001; OR = 5.89; confidence interval = 1.98–17.5) as well as the use of anti-TNF immunotherapy (p = 0.023; OR = 1.10; confidence interval = 1.00–1.14). The main factors that were found to influence the risk of extra-articular disease were age greater than or equal to 60 years (p = 0.008; OR = 4.06; confidence interval = 1.45–11.38), disease duration greater than 10 years (p = 0.031; OR = 3.10; confidence interval = 1.11–8.63) and positive rheumatoid factor (p = 0.035; OR = 2.07; confidence interval = 1.05–4.09).ConclusionsThese results suggest that the TNF2 allele is associated with the more serious forms of the disease in individuals from the Brazilian Amazon but not with a risk for developing RA.