Rheumatic diseases, such as rheumatoid arthritis (RA), lupus and multiple sclerosis, are caused by autoimmune responses. While in immune deficiency disorders the immune system fails to elicit the appropriate immune responses, in autoimmune disorders the immune system overresponds against one’s own antigens. This failure to distinguish between self and nonself arises from breach of immune tolerance, the preventative mechanisms the immune system has in place to prevent attacking itself.1 Autoimmunity could affect specific organs (RA) or they could be systemic (lupus). Some diseases such as ankylosing spondylosis are considered both autoimmune as well as inflammatory arthritic diseases.
Examples of rheumatic diseases
Rheumatoid arthritis (RA) is an autoimmune disorder characterized by inflammation and damage of the joints throughout the body, including hands and feet and affects about 0.5–1% of the population, being more common among women than men in the United States.2 Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease. It affects multiple organ systems, such as the skin, kidneys, lungs and the central nervous system, by producing autoantibodies.3 Ankylosing spondylosis (AS) is a chronic, progressive inflammatory rheumatic disease of the axial musculoskeletal system caused by multiple genes.4
Genetic basis of AS
Genetic factors contribute significantly to rheumatological disease. In particular, the human leukocyte antigen (HLA) locus accounts for about 50% of genetic predisposition to rheumatological disease, with strong involvement of HLA-DRB1, a major histocompatibility complex (MHC) class II molecule.4 Other non-HLA susceptibility genes, such as protein-arginine deiminase type 4 (PADI4) and interleukin-2 receptor subunit α, are also implicated in rheumatological disease. HLA-B27, an MHC class I molecule, has a strong association with AS. HLA-B27 testing is routinely used to screen for ankylosing spondylitis.5,6
