Risk for rheumatic disease in relation to ethnicity and admixture

Risk of systemic lupus erythematosus (SLE) is high in west Africans compare d with Europeans, and risk of rheumatoid arthritis (RA) is high in Native A mericans compared with Europeans. These differences are not accounted for b y differences in allele or haplotype frequencies in the human leucocyte ant igen (HLA) region or any other loci known to influence risk of rheumatic di sease. Where there has been admixture between two or more ethnic groups tha t differ in risk of disease, studies of the relationship of disease risk to proportionate admixture can help to distinguish between genetic and enviro nmental explanations for ethnic differences in disease risk and to map the genes underlying these differences.