The chronic arthropathies of childhood share clinical and pathological features with rheumatoid arthritis (RA) in adults. Both are autoimmune diseases characterized by a destructive arthropathy. Both are likely to be complex genetic traits, with autoantibodies and with a type-1-T-helper-cell cytokine profile in disease tissues. In common with other autoimmune diseases, both have associations and linkage with human keukocyte antigen (HLA) genetic markers. However, there are also important points of distinction outlined in this chapter, which include substantial differences in clinical phenotype. Juvenile rheumatoid arthritis (JRA) is characterized by several subtypes, whereas RA is more homogeneous. There are differences in outcome: adults with RA tend to have a poorer outcome; in JRA, the outcome is more variable and can be predicted by phenotypes at presentation. In addition, patients with RA have a stronger family history of RA although both RA and JRA share an increased frequency of family history of other autoimmune diseases. The genetic markers present to variable degrees in the subtypes of JRA differ quite considerably from those of RA. This is particularly so with respect to HLA.
Prahalad, S., & Glass, D. (2002). Is juvenile rheumatoid arthritis/juvenile idiopathic arthritis different from rheumatoid arthritis? Arthritis Res, 4(Suppl 3), 1–8. https://doi.org/10.1186/ar594