Is Relapsing-Remitting MS Hereditary? Risk & Testing

Relapsing-remitting multiple sclerosis (RRMS) is not strictly hereditary in the way that eye color or conditions like cystic fibrosis are passed down. Instead, MS is a complex disease associated with a combination of genetic susceptibility and environmental factors ^[1][2]. While having a parent or sibling with MS does increase a person’s risk compared to the general population, the vast majority of family members will never develop the condition ^[3][4].

Understanding the Risk for Family Members

MS is a polygenic condition, meaning it involves variations in hundreds of different genes, none of which are strong enough to cause the disease on their own ^[4]. Because no single gene determines whether someone will get MS, there is no simple inheritance pattern. Family history cannot reliably predict whether a relative would develop relapsing-remitting MS versus a progressive form of the disease.

The risk is higher for first-degree relatives (children, siblings, and parents). Research shows that children and siblings of someone with MS have a higher chance of developing the condition than people with no family history ^[3][5]. While specific estimates vary widely based on the study, the country, and the sex of the individuals, the absolute risk remains low. Even with an affected parent or sibling, the vast majority of first-degree relatives will not develop MS ^[6].

The genetic risk is thought to interact with environmental exposures, though the exact causes are not fully understood ^[1]. Developing MS is no one’s fault, and these environmental factors are simply associated with a higher risk:

• Epstein-Barr virus (EBV): Previous infection with this extremely common virus (which causes mononucleosis) is strongly associated with MS risk, though infection alone is not enough to cause the disease ^[7].
• Vitamin D and sunlight: Lower levels of vitamin D and low sunlight exposure are observationally linked to a higher risk of developing MS ^[8][9].
• Smoking: Smoking cigarettes is associated with an increased likelihood of developing MS, especially in people with a genetic susceptibility ^[10][11].
• Adolescent obesity: Being overweight or obese during childhood and adolescence is another associated risk factor ^[12][11].

Should My Children or Siblings Be Tested?

Routine predictive testing—whether genetic testing or MRI scans—is not recommended for children or siblings who feel well and do not have symptoms.

• Genetic Testing: Because MS involves hundreds of genes, currently available genetic tests cannot reliably predict who will develop the disease ^[13]. Knowing a family member’s genetic score would not change their medical management or give a definitive answer about their future health.
• MRI Scans: Routine MRI screening for symptom-free relatives is not established practice. Sometimes, an MRI done for an unrelated reason reveals incidental, MS-like spots in someone with no symptoms—a situation called radiologically isolated syndrome (RIS). RIS is not the same as MS, but discovering it can lead to complex monitoring decisions, debates about early treatment, and unnecessary anxiety ^[14].

When to Seek Medical Advice

Family members should not have MRIs just because of their family history. However, they should seek a doctor’s evaluation if they develop new, unexplained neurologic symptoms.

• Emergency Symptoms: Sudden weakness, trouble speaking, severe imbalance, or sudden vision loss can be medical emergencies (such as a stroke) and require immediate emergency care. Do not wait to see if they persist.
• Other Symptoms: Symptoms like numbness, tingling, vision changes, or balance problems that last more than 24 hours (without a fever or infection) should be evaluated by a clinician.

It is important to remember that many common, less serious conditions can cause these symptoms, so an unexplained symptom should not automatically be assumed to be MS.

What Family Members Can Do

While there is no guaranteed way to prevent MS, family members can focus on healthy lifestyle choices that are good for general health and address some of the associated environmental risk factors ^[11]:

• Don’t smoke: Avoid starting, and quit if you currently smoke. This is excellent for overall health and removes a known MS risk association ^[10].
• Maintain a healthy weight: Encourage a balanced diet and regular exercise to support overall health and help prevent childhood and adolescent obesity ^[12].
• Discuss nutrition and Vitamin D: Have family members discuss general, age-appropriate nutrition and bone health with their doctor. While low vitamin D is linked to MS, it has not been proven that taking high doses of supplements prevents MS in healthy relatives. Testing or supplementation should only be done when clinically indicated by a doctor ^[11][9].