Genetic basis of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a clinically heterogeneous condition with a complex aetiology in which environmental and genetic factors are implicated. The contribution of human leukocyte antigen (HLA) genes, particularly the HLA-DRB1 gene, to RA genetic predisposition was the first described, and remains as the best characterised single genetic risk factor contributing to RA. However, it has been estimated that only 30% of the genetic contribution to RA can be attributed to HLA genes and it is suggested that other non-HLA genes may play a relevant role in RA susceptibility. Linkage studies and association studies are the two main strategies used in the investigation of genetic factors contributing to complex genetic traits. In this work we review the progress made in the field of RA genetics, focusing mainly on the contribution of candidate gene association studies to the dissection of RA genetic risk factors.