What causes RA? Researchers, physicians, epidemiologists, and theologians have devoted an enormous amount of time and energy in trying to answer this question. Despite their efforts over the past one hundred years (since the question was first posed, by Sir Archibald Garrod in 1858, when he named rheumatoid arthritis), no single cause of RA has been identified.
Recent studies have given us some clues to the cause of RA, however. There is evidence, for example, that genetics may play a role in its development. Studies have revealed that one specific genetic marker, called HLA-DR4, appears on the white blood cells of approximately 65 percent of people with RA. RA patients with this genetic marker tend to have more severe arthritis than those without it. However, 25 percent of people with HLA-DR4 have no RA at all, so genes are not the whole story. Other genetic markers are also being studied, with similar results. (Although genes may provide a clue to the cause of RA, most people with RA do not know whether they have these genetic markers. Currently, only physicians who are involved in a university-based research project test for the presence of genetic markers.)
Because not everyone who has the genetic markers described above develops RA, we must consider the possibility that a virus, bacteria, or another substance triggers the development of RA in people made susceptible by their genetic makeup. Over the past century, scientists have searched for a link between hundreds of different infections and the development of RA. (Late in the 1920s, for example, tuberculosis was the suspected culprit.) So far, not one of these scientific studies has proven that a virus, bacteria, or other infectious agent can cause RA.
As with other diseases, one concern is whether someone can “catch” RA from another person. In 1950, two investigators tried to “transmit” RA to volunteers by injecting into their joints fluid taken from the joints of people with RA (Levinski and Lansburg 1951). Because none of the volunteers developed RA, scientists were able to conclude that RA is not a persistent infection of the joints. Although the future may show that an infectious agent triggers the onset of RA, we now know that RA is not infectious or contagious.
Recent scientific studies have focused on viruses as potential triggers for the development of KA in the susceptible person. Epstein-Barr virus for example, has been suggested as a triggering agent for RA. (We already know that Epstein-Barr virus causes mononucleosis, or “mono,” an acute illness affecting young adults which causes fever, sore throat, malaise, and swollen lymph glands.) Investigators will continue to search for the cause of RA, and maybe soon we will identify the causative agent. What is important to keep in mind is that even if an infection does trigger the development of RA, it is impossible to catch RA from someone who has it.
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