Genes Role Small in Rheumatoid Arthritis

[Guest guest]

Genes May Play Small Role in Rheumatoid Arthritis Fri Feb 1, 1:26 PM ET By Mulvihill NEW YORK (Reuters Health) - A small study involving twins suggests that a person's genes play only a minor role in whether or not they will develop rheumatoid arthritis--an autoimmune disease in which the body's tissues are mistakenly attacked by its own immune system. The potentially disabling disease, which affects 2.1 million Americans, causes chronic inflammation and pain of the joints. Even though scientists have been actively investigating rheumatoid arthritis, the cause of the disease is still unknown, according to the study's lead author, Dr. Anders J. Svendsen of Odense University Hospital in Denmark. "Infectious agents such as viruses, bacteria and fungi have long been suspected as causative agents, but none has been found to be responsible for the development of the disease," Svendsen told Reuters Health in an interview. "Many scientists believe that there exists an appreciable genetic component in the causation of the disease, but no single genetic factor has been proven as the cause of the disease," he added. To investigate, Svendsen and colleagues studied 13 identical and 36 fraternal (non-identical) twin pairs in which at least one twin had rheumatoid arthritis. In two of the fraternal twin pairs both siblings were affected, but in none of the identical twin pairs were both siblings affected, the researchers report in the February 2nd issue of British Medical Journal. "So even though (identical) twins have exactly the same genes, only one of the twins developed the disease," he explained. "Thus, our study shows that environmental effects seem to be of pivotal significance in the causation of rheumatoid arthritis, and contrasts the results from previous twin studies on rheumatoid arthritis which have pointed toward a role for the genes," Svendsen added. This study cannot disprove a genetic component in susceptibility to rheumatoid arthritis, Dr. Alan J. Silman of Manchester University Medical School, writes in an accompanying commentary. "However, their results emphasise that the genetic effects are weak compared with environmental ones in explaining differences in occurrence of the disease," Silman adds. SOURCE: British Medical Journal 2002;234:264-267.