Related Experiment Videos
Multiple sclerosis: infectious hypothesis
E Granieri1, I Casetta, M R Tola
1Department of Neurology, University of Ferrara, Italy.
Abstract:
In the search for the etiology of multiple sclerosis (MS), consideration has been given in turn to infectious agents, to genetic markers, and more recently to a combination of genetic and environmental factors, but after over a century of research, a definite conclusion has not been reached. The hypothesis that an infectious agent is responsible for triggering MS is perhaps one of neurology's most enduring notions. Interest in an infectious etiology has waxed and waned over the last two centuries since Pierre Marie first proposed that MS often starts as an infectious process. The possible role of infectious agents has been suggested by: the different geographic gradients in frequency among Caucasians; changes in prevalence due to migration, and the effect of age at migration; the suggestion of epidemics and clusters of cases in some small communities; and the remarkably low degree of concordance in monozygotic twins. The infectious hypothesis is strongly supported by the different temporal patterns of the disease in different geographic areas. Incidence rates have remained stable in some areas, but have changed over time in other regions. On the other hand, the hypothesis is hampered by the lack of evidence for a specific agent, and the weakness of the results of analytical studies that have tested the association between MS and previous infections. Despite these drawbacks, recent studies of a few select pathogens suggest that viral or bacterial infections or reactivations may trigger clinical exacerbations in relapsing-remitting MS.
Insights
The cause of multiple sclerosis (MS) remains elusive, with infectious agents proposed but lacking definitive proof. Recent research suggests infections may trigger relapses in existing MS cases.
Area of Science:
- Neurology
- Epidemiology
Background:
- The etiology of multiple sclerosis (MS) has been investigated for over a century, with infectious agents, genetic factors, and environmental influences proposed.
- The hypothesis of an infectious trigger for MS has persisted despite a lack of conclusive evidence.
Purpose of the Study:
- To review the evidence supporting and refuting an infectious etiology for multiple sclerosis.
- To explore the potential role of infections in triggering MS exacerbations.
Main Methods:
- Review of historical and recent epidemiological studies on MS.
- Analysis of factors such as geographic variation, migration patterns, and twin concordance.
- Examination of studies investigating associations between MS and specific pathogens.
Main Results:
- Geographic gradients, migration effects, and temporal incidence changes suggest environmental or infectious factors.
- Low concordance in monozygotic twins and observed clusters hint at external triggers.
- Despite suggestive epidemiological data, a specific infectious agent has not been identified, and analytical studies show weak associations.
- Recent findings indicate that viral or bacterial infections may precipitate relapses in relapsing-remitting MS.
Conclusions:
- The infectious hypothesis for MS etiology remains plausible but unproven.
- While a definitive causative agent is elusive, infections may play a role in triggering MS relapses.