Causes and risk factors in Multiple Sclerosis

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Multiple sclerosis is a disease of unknown cause in which, probably, an environmental factor induces an abnormal immune response in a genetically predisposed individual.

The immune system recognises one of the patient’s own proteins as foreign and thus destroys the myelin (fatty material that covers and protects the nerve fibres of the brain and spinal cord), the oligodendrocytes and, secondarily, the nerve fibres (axons).

Risk factors in Multiple Sclerosis

Environmental factors in multiple sclerosis


North-south gradient. When further away from the equator, more frequent. White Caucasians, especially those who have ancestors from the north of Europe, have a higher risk than individuals of Asiatic, African, or native descent.

couple with travel luggage

In immigrants, the presentation frequency differs from that of their parents. If someone emigrates before 15 years of age from a country with a low frequency to another of a high frequency, the risk is the same as the indigenous population.

Vitamin D

High levels of vitamin D and sunlight.


Virus infections. Several epidemiological studies associate the Epstein-Barr virus, which causes infectious mononucleosis, with multiple sclerosis.


Tobacco. Is associated with developing it and with the earlier appearance of the progressive secondary form of the disease.

Genetic factors in multiple sclerosis

Multiple sclerosis is not hereditary, but there is a certain genetic disposition. For the general population with no affected relatives, the risk is 1 case for every 1,000 inhabitants; for first-degree relative of an individual affected, such as son/daughter, brother/sister, or non-identical twins, the risk is from 2.5 to 5 cases per 100 inhabitants, and in the case of both parents being affected it increases to 20 per 100 inhabitants.

Substantiated information by:

Albert Saiz Hinarejos
Ana Hernando Andrés

Published: 20 February 2018
Updated: 20 February 2018


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