The Genetics of Multiple Sclerosis and other Autoimmune Diseases

Many diseases arise from what are termed “autoimmune responses” in which the body turns against itself, targeting its very own cells and tissue and destabilizing its role in protecting the body against infection and foreign bodies – it is essentially the responses of an organism against its own healthy cells and tissues. This atypical autoimmune response is characteristic of a range of diseases which includes Lupus, Celiac disease and Multiple sclerosis (MS). Many autoimmune diseases are known to have a genetic link and people carrying these genes have an increased susceptibility to the disease of which genes play a determining role (along with environmental factors) in the onset of the illness. Let us take a look at one of the more debilitating autoimmune diseases of which epidemiological studies show a relatively high incidence rate in Western cultures: Multiple sclerosis.

Around 2,500,000 people are believed to be affected by this illness and women are affected more than men.  In the USA, it is estimated that there are around 350000 sufferers with a whopping $10 billion in health-bearing costs associated with multiple sclerosis (source: www.easydna.ca). The number of people actually affected is obviously much higher than the cited figures. Figures provided are very loose; they do not in any way reflect or include statistics from underdeveloped countries, which are rather difficult to come by if not altogether absent.

So what is Multiple Sclerosis?

Multiple sclerosis causes the progressive deterioration of the myelin sheath, directly affecting the CNS, the central nervous system (the CNS is comprised of the brain and the spinal cord). The myelin sheath, a plasma membrane, which surrounds axons and nerve fibers plays an important role as an insulator for the electrical impulses generated by the body. The movement of electrical impulses generated by the body is made more efficient and rapid thanks to the myelin sheaths which plays such an important role in facilitating the passage of impulses, helping then travel at higher speeds. Multiple sclerosis however, directly affects the myelin sheath by causing it to break down. As the myelin sheath degrades, the transmission of electrical impulses is impaired if not altogether inhibited. This causes a break down or slowing down in the communication of messages between the brain and the spinal cord and brain stem.

The irreversible damage to the nerves causes what is known as sclerosis of the tissue. Sclerosis is a medical term referring to the formation of scar tissue around the nerves. The formation of scar tissue is due to a process known as demyelination:  the aforementioned deterioration of the myelin sheath. Importantly, although we have just described the process of demyelination as irreversible this is not to say that the myelin sheath cannot regenerate or be replaced with a new myelin membrane. The problem with MS is that the rate at which the sheath is worm away is much higher than the rate at which the sheath can regenerate.

Symptoms

Initially sufferers begin to experience difficult carrying out simple movements such as walking. Pins and needles are also typical of people suffering from this disease. Eventually this chronic illness leads to more debilitating effects including stiffness, inefficient breathing, difficulty balancing and many more.  Acute, chronic pain makes the disease very incapacitating for the person afflicted with MS. Whilst some cases of MS appear to be due to infectious bacteria or viruses which can cause demyelination, the links and correlation between the disease and infections are still being investigated.  Living with MS is not easy – both for the sufferer and for their loved ones. Many support groups, such as the Multiple Sclerosis Society, are available to alleviate the burden of living with the condition and provide guidance and help.

There are several medicines and treatments including alternative medicine, physiotherapy as well as the administration of Corticosteroids or plasma exchange. Treatments may be used to control the condition and to some extent impede its progression but not entirely stop it from progressing. There is no actual cure for MS.

So where do the genetic links lie?

Multiple sclerosis does appear to run in families but whether this disease is actually hereditary has not been established. Scientists have however, found a number of genetic variations which appear to increase ones genetic predisposition to the illness. The genetic links appear to be strong but it is hard to determine whether these carry more weight in disease onset than environmental factors.

Studies have suggested that people with direct blood relatives who have suffered from multiple sclerosis are up to 7 times more likely to suffer from the disease. Studies have also based themselves upon monozygotic twin studies (identical twins) to determine the incidence rate of the disease amongst twins with identical DNA profiles. The fact that when one identical twin has MS, the other twin has a 30% chance of also developing the illness does suggest the possibility of a hereditary aspect to the disease.

Attempts to find specific links and gene variations responsible for MS have been produced by many studies. Several of these have focused their efforts and analysis on chromosome 6 – a chromosome which they believe to account for around 8% of all cases of genetic MS. The HLA (HLA standing for Human Leukocyte Antigen) gene is also linked to MS. There have been other studies which have singled out other chromosomes involved in MS namely 3, 5, and 19.

Genetic predisposition DNA testing for multiple sclerosis is also readily available by many online testing companies such as homeDNAdirect, 23andMe and private clinics. These are essentially tests to determine how likely an individual is of developing multiple sclerosis over the course of their life. Somebody with a high genetic susceptibility to multiple sclerosis is more likely to develop the diseases if they encounter an environmental trigger such as a virus. A DNA test can help build awareness and possibly reduce any anxiety caused for those who have a history of MS in the family. One could either find out they have a low or nonexistent predisposition to MS or perhaps discover they have a very high predisposition which would itself suggest that they have inherited the diseases causing genetic mutation.

Certain basically dietary and lifestyle habits can help reduce (although not eliminate) your chances of developing MS. Getting enough vitamin D for example is believed to be crucial; in fact the prevalence of multiple sclerosis is less amongst people living close to the equator than people in Northern countries such as Sweden. Smoking can also be a factor, especially amongst the many of us who have been exposed to the Epstein Barr virus. Dairy products and obesity are also linked to MS – you might want to reduce your diary intake and undertake a regime to control your weight and keep it within optimal parameters, especially if a genetic health test confirms a high genetic suspect ability to multiple sclerosis.