Genetic epidemiology of rheumatoid arthritis: what to expect from Latin America?
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Rheumatoid arthritis is a chronic and systemic autoimmune disease characterized by inflammation and destruction of the synovial joints. It affects approximately 0.5% of the Latin-American population and is three times more common in women than in men. Evidence of familial aggregation (lambdas=2-17) was the first indication of a genetic susceptibility to disease. As in other autoimmune diseases, it has a complex genetic basis. Results from whole-genome scans indicate that the HLA region contains a significant and consistent set of linked loci. However, HLA accounts for only one-third of the genetic susceptibility of disease, indicating that non-HLA genes are also involved in the disease susceptibility. In Latin-America, association with HLA-DRB1*0404 and TNF -308A alleles has been uniformly established; however, many other candidate genes remain to be studied. The identification of genetic factors conferring susceptibility to rheumatoid arthritis will contribute to the knowledge of the pathogenic mechanisms, ability to predict its occurrence, the development of diagnostic tools, prognosis, and treatment. The genetic epidemiology of rheumatoid arthritis is herein reviewed; a set of recommendations is provided for the design, analysis and interpretation of genetic association studies in the context of Latin-American populations.