A study of the haplotypes of the TNFA rs1800629 and LTA rs909253 loci showed a tendency towards a rarer occurrence of the A-G haplotype in JIA patients with the insufficient response to methotrexate than in those with the sufficient (7.20% vs. 11.87%, respectively, P = 0.082). This evidence concerns the gene TNF and juvenile idiopathic arthritis.