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When a patient is first diagnosed with rheumatoid arthritis, they often ask themselves "Why me?” Perhaps if we knew the cause of the disease, then we might be able to stop it in its tracks.
Of course, few things in life are quite that simple. Researchers have known for many years that the causes of rheumatoid disease are multi-factorial. In other words, a number of different factors come together in one individual to create the circumstances necessary to trigger the onset of the disease. A recent research paper in the British Medical Journal (Svendsen et al. BMJ 2002; 324: 264-7) has locked at the relative importance of environmental and genetic factors in the development of rheumatoid arthritis.
These researchers, from Denmark, have looked at twins to see how important genes are in the development of RA. By comparing identical and non-identical twins with rheumatoid arthritis, they have attempted to separate the influence of genes and environment from one another.
Identical twins who are brought up in the same household share exactly the same genes and virtually the same environment, at least until they leave the family home. By contrast, non-identical twins share only a proportion of their parents' genes, although their environmental influences should be just as similar as that of identical twins.
This study looked at two groups of Danish twins. The first group comprised 2,445 twins born between 1921 and 1940 whilst the second consisted of 29,433 twins born between 1953 and 1982. Just 49 patients were found to have rheumatoid arthritis and the disease was no more common amongst the identical twins than it was amongst the onon-identical. The authors concluded that genes are of minor importance in the development of rheumatoid arthritis and probably less important than environmental factors.
In the same issue of the journal, Professor Alan Silman of Manchester University discusses these findings in the light of previous research. Two previous twin studies from Finland and the UK showed some genetic contribution to the development of rheumatoid arthritis which was in contrast to the results of the Danish group. He explains that there may be technical reasons for the differences in these results but that overall, they "emphasize that the genetic effects are weak compared with environmental ones in explaining differences in occurrence of the disease".
Perhaps this challenges some popular pre-conceptions about the cause of rheumatoid arthritis, but we should not be too discouraged by these findings. It may be true that "you can't pick your parents", but if the majority of the factors which cause rheumatoid arthritis are environmental, then perhaps we have a better chance of ultimately preventing the development of this crippling disease. | Thanks for the article. Maybe genes just give us a predisposition for the disease. Allergies are genetic, and if you think about it, what is an allergy? One's immune system is reacting or attacking something that it shouldn't. So, if we have inherited this "hypersensitive" immune system or allergy, and then if we are very stressed, or pregnant, or sick, or for some other reason our immune system is down and we encounter something environmental that we are allergic to, say a bacteria, virus, parasite, fungus, mycobacteria, mycoplasma, L-form, etc, and we are "allergic" to that environmental trigger-- that might set off the RA symtoms.I have RA, as does a male cousin, another relative in
scotland has it, my gt.grandfather also had it according to his death certificate and we are not a close family!
Seems like a few coincidences if it is not genetic.
Mono- and dizygotic twin studies can be difficult to get conclusive results from. One would think think that monozygotic twins raised in the same environment would give a good indication of genetic or environmental factors involved in disease processes but they frequently don't. One of the best research methods for this are genetic studies with monozygotic twins, separated at birth and raised with different parents. This way the genetics of the birth mother, birth father where available and children can be considered on an individual basis. If both twins develop the disease despite being raised in separate environments then the concordance rate for genetic prevelance is very high If not, it's very low.
Personally, I'm of the opinion that some people have a genetic predisposition towards autoimmune diseases and the disease is triggered by an environmental factor. I have relatives on both sides of the family with RA and/or MS. This and similar research has been going on for years and they always come to the same conclusion which is "we don't know".
Unfortunately, such a small group--49? had RA that it doesn't seem
conclusive for anything.
So many families have different auto immune diseases that focusing on just
RA, instead of including MS and lupus-pretty much eliminates more than
half the related genes. Why didn't they check for all of the auto-immune
diseases or at least the thyroid one that is so very common.
and so "we don't know"
Bee
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