What causes multiple sclerosis? Is it hereditary?

Although multiple sclerosis was described by Charcot over a century and a half ago, the causes of this disease of the central nervous system are still unknown.
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Although multiple sclerosis was described by Charcot over a century and a half ago, the causes of this disease of the central nervous system are still unknown

Genetic factors

Multiple sclerosis (MS) is not a hereditary disease. It is a condition with a multifactorial origin. Certain environmental factors have now been identified, although a causal relationship has not yet been clearly established. There may also be a genetic predisposition. This can be defined as a combination of genetic variants that confer a greater risk of developing the disease. Genetic predisposition alone is not considered to be sufficient for the disease to appear, but rather to provide a favourable environment for its development. It should be noted that most of the genetic variants identified are associated with so-called “immune” genes, i.e. those involved in inflammation.


Environmental factors

Epidemiological studies have not identified a definite environmental factor responsible for triggering the disease. A vitamin D deficiency could be a triggering factor, but its involvement has yet to be definitively proven. Numerous viruses have also been studied, with the hypothesis that a viral infection contracted in early childhood could be the cause of the disease in genetically predisposed individuals.

The link between multiple sclerosis and infection with the Epstein-Barr virus has long been suspected. Very recently, an American study has provided important new information on this association. The Epstein-Barr virus belongs to the herpes virus family. Most often contracted asymptomatically in childhood, it is also responsible for infectious mononucleosis or “kissing disease”. The Epstein-Barr virus is widespread in the general population, with an estimated 90% of adults having been in contact with the virus. This infection therefore seems to be a necessary but not sufficient condition for developing multiple sclerosis. The vast majority of people infected with the Epstein-Barr virus will never develop multiple sclerosis.


No link between vaccination and multiple sclerosis

Long blamed for the onset of multiple sclerosis (MS), vaccines have been the subject of large-scale epidemiological studies. Two million young girls vaccinated against HPV were monitored over several years as part of a study conducted by the French National Agency for the Safety of Medicines and Health Products. The study concluded that the occurrence of multiple sclerosis in these young girls was no more frequent than in the general population. Several studies on the relationship between the hepatitis B vaccine and the onset of multiple sclerosis have reached the same conclusions.


At the Paris Brain Institute

The International Multiple Sclerosis Genetics Consortium (IMSGC), involving a research team from the Institut du Cerveau, published a scientific article in the journal Science in 2019 bringing the number of genetic variants predisposing to multiple sclerosis to 233. The study involved 47,429 patients and 68,374 controls. These results confirm that multiple sclerosis results from a dysfunction of the immune system and pave the way for functional research into the causes of the disease.


Last updated May 2024.