What is Multiple Sclerosis?
Multiple sclerosis is characterised as a long-term disease that affects your brain, spinal cord and your eyes, resulting problems with vision, balance, muscle control and other functions.
The effects of the disease differ from person to person, some are mild with no treatment required, while others can make it hard to do basic tasks.
It occurs when the immune system attacks Myelin, a fatty material that wraps around your nerve fibres to protect them, so damage to them can cause damage to your nerves resulting in the formation of scar tissues.
This prevents your brain from sending signals through your body correctly so your nerves do not work properly, resulting in a variety of symptoms which include having trouble walking, having a feeling of fatigue, muscle weakness and spasms, blurred or double vision, numbness and tingling, along with a number of mental issues such as depression and memory problems.
It is possible for people who have had Multiple Sclerosis and relapse after a time of recovery, or their symptoms may get worse as time goes on.
The role of genetics in multiple sclerosis
The overall cause of Multiple Sclerosis is unknown. It can affect some people and not others. One possibility is that genetics may play a significant role in whether or not somebody is affected by the disease.
According to the Multiple Sclerosis society of Ireland, the disease cannot be directly inherited. However, a combination of genes that are widely distributed among the population, can increase your risk of developing the disease.
So genetics are not the only factor that determines the development of multiple sclerosis, and although it may occur multiple times in a single family, the chance of a child developing the disease as a result of a parent or relative having it, is only 2% to 5%.
Looking at the various genetic factors that increase the disease, it is clear that changes in the HLA-DRB1 gene are the strongest risk factor in terms of genetics as the HLA complex normally ensures that the immune system is able to differentiate between proteins native to the body, and that of possible invaders.
However, certain variations of the gene have been associated with an increased risk in developing Multiple Sclerosis. For instance, the HLA-DRB1*15:01 gene has been a linked to be a strong risk factor for developing Multiple Sclerosis.
Another genetic risk factor includes the IL7R gene which instructs parts of the two receptor proteins which are the interleukin 7 (IL-7) receptor and the thymic stromal lymphopoietin (TSLP) receptor.
These are embedded within the membrane of immune cells, stimulating pathways that will induce the growth, division and survival of immune cells.
Variations of this gene however, can result in the production of an unknown IL-7 receptor (as it is not embedded in the membrane of a cell, but is found within one), which can have an effect on the TSLP receptor which can increase the risk factor for Multiple Sclerosis.
Looking at these variations, it can be seen that they increase the risk of someone developing Multiple Sclerosis as they are both involved in the immune system.
As a result, detrimental variations can result in changes to the autoimmune response. This change can cause damage to the myelin sheath which can lead to the emergence of various symptoms related to Multiple Sclerosis.
However, it is not clear as to what role gene variations play in the development of Multiple Sclerosis. Other genes that may be related to Multiple Sclerosis include CYP27B1, HLA-DRB1, IL2RA, IL7R and TNFRSF1A.
Role of familial inheritance
Apart from genetic variation, WebMD notes that there has been speculation among researchers with regards the possibility that Multiple Sclerosis could be inherited from other family members.
It is possible that first, second and third degree relatives of people who have been previously affected by Multiple Sclerosis are at an increased risk of developing it, with the risk factor currently ranging from 2% to 5%.
WebMD also states that people can be born with a particular gene that can trigger an autoimmune response as a result of a certain environmental factor, thus bring about the development of Multiple Sclerosis.
Other factors in the development of Multiple Sclerosis
Aside from genetics and inheritance, there are a number of other factors that increase the risk of developing Multiple Sclerosis.
Age can be a risk factor as Multiple Sclerosis can start to affect people who are between the ages of 20 and 40. Past viral infections may affect one’s risk of getting the disease.
For example, the Epstein-Barr virus or the human herpesvirus 6 can cause the immune system to operate incorrectly.
In addition to increasing your risk of getting the disease, viral infections can also trigger relapses in Multiple Sclerosis. However, scientists do not have a clear answer for the link between viruses and Multiple Sclerosis.
Vitamin D deficiency can be another risk factor that determines your chances of getting Multiple Sclerosis as Vitamin D can help strengthen your immune system and can ensure that you are protected from the disease.
WebMD notes that people who are high risk that move to sunnier regions tend to lower their risk of getting Multiple Sclerosis. Smoking plays a role in increasing the chances of developing Multiple Sclerosis and can lead to a more rapid progression and a much more severe disease.
Very much like the effect of an increase in Vitamin D, when a person stops smoking, they slow down the progression of the disease.
In conclusion, while genetics and inheritance may not play a direct role in the development of Multiple Sclerosis, they act as important risk factors in terms of getting the disease.
Variations of important genes that operate within the immune system can result in an incorrect immune response that damages the Myelin, thus bringing about the onset of Multiple Sclerosis.
Familial inheritance is another risk factor, but the risk is much lower, only ranging between 2% to 5%.
It should be noted that there are a number of other risk factors associated with the onset of Multiple Sclerosis such as smoking, age, vitamin D deficiency and past viral infections.