The fact that a person has developed kissing disease does not necessarily mean that they will develop multiple sclerosis.

Given the information that has recently appeared in the media indicating that the virus that causes the kissing disease or infectious mononucleosis (Epstein-Barr virus) is responsible for multiple sclerosis, the SSpanish Society of Neurology sent a statement with important clarifications:

What is multiple sclerosis

THE multiple sclerosis is a chronic autoimmune, inflammatory and degenerative disease of the central nervous system, being the most common non-traumatic disabling neurological disorder in young adults in developed countries.

The most recent prevalence studies indicate that the frequency of the disease has increased in the world in recent decades, that this increase in prevalence is fundamentally at the expense of a greater number of cases of women with relapsing-remitting forms, and that the influence of the gradient latitudinal appears to be attenuating.

Currently, it is estimated that there are approximately 2.5-3 million patients worldwide and about 55,000 in Spain. The disease is typical of women (3 cases for every male case) and usually starts between 20 and 40 years old.

It’s not just a genetic disease

Currently, the cause of multiple sclerosis is unknown, although most studies support the existence of environmental factors that, acting in genetically predisposed individuals, trigger the autoimmune phenomenon through which inflammatory and degenerative processes develop in the central nervous system.

The influence of these environmental factors seems to be crucial during childhood, as shown by studies carried out in populations that migrate from areas with low frequency of the disease to others with high risk, or vice versa, and may modify the susceptibility of suffering from the disease in such a way that both first decades of life seem fundamental to establish the risk of suffering from multiple sclerosis.

The disease does not follow a conventional inheritance pattern, associated with a single gene, but more than 200 genes have been identified that seem to give the individual a greater risk of developing it when exposed to the aforementioned environmental factors.

Many studies have been carried out to try to identify which, or which, are the environmental factors directly related to the development of the disease without, so far, having been able to establish a definitively consistent relationship with any of them.

Viruses acquired in adolescence

Among these environmental factors, vitamin D levels have been studied in direct relation to exposure to ultraviolet radiation from sunlight, smoking, salt consumption, obesity in adolescence and exposure to various infectious agents such as the Epstein Barr virus (EBV).

For many years, it has been proposed that infectious agents exist that would increase the risk of multiple sclerosis if acquired in adolescence, but not if first contact with them occurs in childhood.

Supporting this “hygiene theory” hypothesis, epidemiological findings indicate that the prevalence of the disease is low in developing countries and tends to increase in regions with higher socioeconomic status and sanitation, where the age of these primary infections is delayed.

Interestingly, the timing of primary EBV infection is generally considered a marker of infant hygiene and has been associated with an increased risk of developing multiple sclerosis.

Usually acquired in early childhood in developing countries, primary EBV infection is dramatically delayed in developed areas, with a much lower seroprevalence in young people, so that when this occurs, the risk of developing infectious mononucleosis significantly increases, while in childhood the infection can present a very banal or even asymptomatic clinical presentation.

Infectious mononucleosis is an important risk factor

Although several studies provide strong evidence that infectious mononucleosis is an important risk factor for the development of MS, it is also true that the very high prevalence of EBV seropositivity in the general population (95%) and the relatively low frequency of incidence of multiple sclerosis pose a major challenge to prove direct causality between the risk of developing the disease and previous viral infection.

In summary, EBV infection before age 15 years can influence the risk of developing multiple sclerosis and this age dependence may be due to altered immune responses after contact with the virus in adolescence and early adulthood, but the fact that a having developed an infection with this virus does not necessarily imply that they develop multiple sclerosis, as, as we pointed out earlier, the disease is multifactorial.

Despite the study recently published in the journal ‘Science’, in which, again, a possible association between the Epstein-Barr virus and multiple sclerosis appears to have been found, it is not clear why multiple sclerosis manifests itself in some people and in others. do not. .

Thus, we reiterate that research continues to point to a combination of genetic factors with other environmental factors and not just a single factor.

information or Dr. Miguel Ángel Llaneza, Coordinator of the Study Group on Demyelinating Diseases of the Spanish Society of Neurology (SEN)

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