JRA is more common in Caucasian children than in African-American or Asian American children. One study found that African-American children diagnosed with JRA were older at onset of symptoms of JRA than Caucasian children. Like adult rheumatoid arthritis, juvenile rheumatoid arthritis is an autoimmune disease, which means the body's immune system attacks its own healthy cells and tissues. JRA is considered to be a multifactorial condition. The factors are usually both genetic and environmental, where a combination of genes from both parents, in addition to unknown environmental factors, produce the trait or condition.
Multifactorial traits do recur in families because they are partly caused by genes.
A group of genes on chromosome 6 codes for the HLA antigens play a major role in susceptibility and resistance to disease. Specific HLA antigens influence the development of many common disorders. Some of these disorders, like JRA, are autoimmune related and inherited in a multifactorial manner. The HLA antigen associated with JRA is called DR4. This means HLA antigen testing is not diagnostic or accurate for prediction of the condition.