Etiology and pathology of multiple sclerosis

1. Big picture

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by multifocal demyelinating plaques, inflammation, gliosis/scarring, and axonal degeneration.

The key exam idea:

MS is not simply “loss of myelin.” It is an immune-mediated CNS disease with inflammation, demyelination, oligodendrocyte injury, partial remyelination, gliosis, and progressive axonal loss.

The etiology is still not completely known, but MS is best understood as a multifactorial disease developing in genetically susceptible individuals exposed to environmental and immunological triggers.

The most important risk factors are:

• young adult age;
• female sex;
• Northern European/white ancestry;
• higher latitude;
• genetic susceptibility, especially HLA-DRB1*15:01;
• Epstein-Barr virus exposure;
• low vitamin D / low sunlight exposure;
• smoking;
• family history.

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