Multiple Sclerosis (MS) is a chronic condition affecting the central nervous system. While MS is not directly inherited, a family history indicates a shared genetic background that can increase susceptibility. Understanding your risk involves looking at the disease itself, the role of genetics, and the influence of non-genetic factors.
What is Multiple Sclerosis?
Multiple Sclerosis (MS) is an autoimmune disorder where the immune system mistakenly attacks the central nervous system, which includes the brain and spinal cord. Immune cells target the myelin sheath, a fatty layer that insulates nerve fibers and allows for rapid signal transmission. This attack causes inflammation and damage, stripping the myelin away in patches, a process called demyelination. The resulting damage creates scar tissue, or sclerosis, which disrupts the flow of electrical signals throughout the body. Symptoms are highly variable, often including fatigue, vision problems, loss of balance, and difficulty with mobility.
The Role of Genetics in MS Susceptibility
MS is categorized as a complex disease, arising from the interaction of multiple genes and environmental factors, rather than a single inherited gene. Researchers have identified over 200 genetic variations that each contribute a small degree to overall risk, known as polygenic risk. The most significant genetic marker associated with MS is found within the human leukocyte antigen (HLA) complex on chromosome 6. This complex helps the immune system distinguish between the body’s own cells and foreign invaders. One specific variant, HLA-DRB115:01, is consistently linked to a higher risk of developing MS. Carrying this gene variant alone does not guarantee the disease, but it does increase the genetic predisposition.
Defining Risk Based on Familial Relationship
The risk of developing MS in the general population is low, estimated at 0.1% to 0.3%. Having an affected family member increases this baseline risk, but the magnitude depends on the closeness of the relationship. Relatives are categorized as first-degree (parents, siblings, children) or second-degree (aunts, uncles, grandparents, and cousins). Your aunt is a second-degree relative, and having MS increases your risk slightly above the general population. For an individual with an affected aunt or uncle, the lifetime risk is estimated to be around 1%. This is much lower than the 3% to 5% risk seen in first-degree relatives. This distinction underscores the polygenic nature of MS, where the number of shared susceptibility genes is the main factor determining familial risk.
Environmental and Lifestyle Risk Factors
Genetics accounts for only part of the overall risk, and environmental factors play a significant co-contributing role in MS development. The interplay between genetic susceptibility and external influences is thought to be the cause of the disease. These non-genetic factors often exert their influence during childhood and adolescence. One established factor is insufficient sun exposure and subsequently low Vitamin D levels, which are linked to an increased risk of MS. A history of infection with the Epstein-Barr Virus (EBV) has also been strongly associated with an increased MS risk. Other modifiable lifestyle factors include smoking, which approximately doubles the risk, and adolescent obesity. Focusing on maintaining adequate Vitamin D levels, avoiding smoking, and managing weight are the primary actionable steps for individuals concerned about their overall risk.