A to Z of MS Causes of MS
Almost 150 years after the condition was first recognised, the cause of MS remains a mystery. The theory that is widely held is that MS is an autoimmune disease. An autoimmune disease is one in which the immune system, which should only target invading germs, turns on the body's own tissues. In the case of MS, the immune system attacks the nerve coverings in the central nervous system.
The reason for this reaction is unknown but it is thought that the genetic make up of some people means that MS can be triggered by an environmental factor, possibly an infectious agent or agents.
Genetics
Although there are instances of several family members developing MS, MS is not hereditary and the majority of people who develop MS have no previous family history of the condition.
The rate of MS within families suggests that there is a genetic factor involved in developing the condition, but studies of identical twins show that genes are not the whole story. Identical twins have exactly the same genetic make up. If MS were solely dependent on genes, it would be expected that if one identical twin developed the condition, so would the other. Studies have shown that rather than this 1 in 1 risk, the actual risk of developing MS for the identical twin of someone with MS is about 1 in 3.
This suggests that there is some other factor that causes some people with a particular genetic make up to go on to develop MS. It is currently thought that this might be an infection of some sort.
Infection
In the early part of the twentieth century research was focussed on the idea that MS was directly caused by an infectious agent. This work failed to find any positive results. Subsequent research, which still continues, has worked on the theory that, rather than being an immediate cause, an infection acts as a trigger which sets off a train of events in some people that develops into MS over a period of time.
A number of viruses have been investigated, including chicken pox, measles, mumps, canine distemper and a number of herpes viruses. Recent research has been looking at the Epstein Barr virus, a common virus that causes glandular fever. However, as yet, if there is a particular virus or combination of viruses, they still have to be identified.