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Last updated Wednesday, September 14, 2005
Causes
Rheumatoid arthritis is not inherited in the usual sense. That is, it is not passed directly from parents to children. A susceptibility or tendency to develop RA can be inherited, but other factors (currently under intense study) also are important. The gene that influences the likelihood or a tendency to have RA is one of the genes that controls the function of the immune system called the HLA-DR4 gene. However, not everyone who inherits this gene will develop the disease.
Many physicians and scientists believe that RA might be triggered by an infection, but there is presently no proof that this is fact. Rheumatoid arthritis is not contagious. It is possible that a germ to which everyone is exposed causes the body's immune system to react abnormally in individuals who are susceptible to rheumatoid arthritis.
In RA, the white blood cells of the immune system move from the bloodstream into the joint tissues. Joint fluid may increase, and the white cells are found in the fluid as well. The white cells in the joint tissue and fluid produce many substances, including antibodies and other molecules, that lead to the joint damage and the sick feeling that occurs in people with rheumatoid arthritis.
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