Is Multiple Sclerosis Genetically Inherited?
Multiple sclerosis (MS) affects close to 2.5 million people worldwide. Chances are you or someone you know has been affected by this condition.
MS is a serious debilitating disease mostly diagnosed from early to mid adult-hood. While treatment can relief the worsening of symptoms, there is unfortunately no cure yet. No one is sure what causes MS, but studies have shown that genetic, immunological and environmental factors are involved.
So, Is MS Genetically inherited?
Are you more likely to develop MS than the general population if a member of your family has MS? If so, is it purely due to genetics? Or do environmental factors also play a role?
To look for answers to these questions, researchers have used genetic epidemiological approaches – Studies that recruit families in which at least one individual has MS to try to see if hereditary is involved in the disease susceptibility.
A Nationwide Study published in 2005 included over 19000 first-degree relatives of Danish MS patients such as parents, children and siblings. Scientists found that first-degree relatives of MS patients had an increase risk of developing MS compared to the general population .
According the National MS society, 1 out of 750 people develop MS in the US general population. For anyone who has a first-degree relative with MS, the risk increases to 1 out of 40. The risk may increase further for those who have more than one relative with the disease .
Do you know a family where more than one person has MS? Vote and view the results.
Is the risk of MS completely genetic? Maybe this higher within-family-risk is rather due to environmental factors. These are important questions because family members living together are usually exposed to similar environmental factors.
To investigate this environmental factors, researchers looked at people living together sharing the same family environment. The only difference being that they were not biologically related such as adopted siblings.
In a population-based study with a sample size of 15000 MS patients, researchers showed that the risk for non-biological relatives of an MS patient was not greater than that of the general (Canadian) population. But the risk for a biological relative was significantly more than that of the general (Canadian) population and non-biological relatives .
Genetic Factor Linked to MS
Scientists have consistently shown that MS occurs more frequently within family members sharing genetic material with an MS patient. First degree relatives such as parents, children and siblings of MS patients develop the disease more often than distant relatives -- the amount of genetic material you share is related to the risk to develop the disease. In other words, the more genes you share with an MS patient, the higher the risk of you getting the disease. There is therefore a strong genetic component involved.
Experts believe there are many genes involved in MS. Alleles of the gene HLA-DRB1 is thought to be associated with MS .
HLA-DRB1 (official symbol) is part of a group of genes called Human Leukocyte Antigen (HLA) complex. The HLA complex helps our immune system distinguish the body’s own proteins from those made by foreign invaders such as microbes. Because of the critical role these genes play in the immune system, changes in them might be linked to damage of the myelin sheath and nerve cells through an autoimmune response.
HLA-DRB1 changes have been reported as one of the strongest genetic risk factors for developing MS. Many other gene variants that are implicated in the risk for MS have been spotted. These include CYP27B1, HLA-DRB1, IL2RA, IL7R and TNFRSF1A).
Environmental Factors Linked to MS
There have been considerable arguments over the years whether environmental factors rather than genetic factor can be associated with MS. It has become apparent to authorities that both factors are associated with MS and they may interact with each other.
Even though the cause of MS is unknown, twin studies have shed some light on factors that may be involved. Identical twins share 100% of their genetic material. Hence if one twin has MS, one would expect the risk for the other to have MS to be 100%. However, this is not the case. In fact the chance for one twin having MS if the other has the disease is about 31% . This suggests that MS is not entirely a genetic disease and that other factors also contribute.
Some environmental Risk Factors that may be potential triggers for MS are Epstein-Barr virus infection, Vitamin D, Sunshine and smoking.
Epstein-Barr virus (EBV) Infection: EBV is a herpes virus that is known to cause several medical conditions. Scientists believe that infection with EBV is an important contributor to MS risk, increasing it by more than 3 folds. Therefore your MS risk would increase when you become EBV positive.
Sunlight and Vitamin D deficiency: Strong evidence has been found implicating vitamin D and sunlight in MS susceptibility. MS becomes more common as you move away from the equator. Hence the disease is believed to be highly correlated with sunshine [review map above]. That is, the more sunshine a region receives, the lesser its frequency of MS.
Sunlight is our main source of vitamin D. A study was conducted within the US military in which researchers obtained samples from military member prior to them developing MS. Vitamin D levels in those samples were measured. Deficiency in vitamin D was found to be accompanied by a high risk of developing MS.
Smoking: We all know that smoking is bad for several reasons. It turns out smoking is worst for people with MS. An interesting research has shown that MS progression is more likely being a smoker. The smoking patterns of patients with MS was analysed together with the way their disease progressed. The disease progression after onset of was found to increase with the degree of smoking.
MS is referred to as a complex disease because it is associated with several risk factors and probably an element of chance. Is MS genetic? It can be said that both genetic and non-genetic factors are involved in MS.
This is an interesting interview with Professor Anne-Louise Ponsonby on what triggers Multiple Sclerosis.