Rheumatoid arthritis (RA) is a chronic autoimmune disease in which dysregulated interferon regulatory factor 5 (IRF5) may amplify pro-inflammatory pathways; prior genetic studies of IRF5 single-nucleotide variants (SNVs) in RA are inconsistent across populations and have not included mestizo Mexicans or evaluated rs59110799 in RA. This evidence concerns the gene IRF5 and rheumatoid arthritis.