Multiple sclerosis (MS) is a chronic, neurological disease, typically progressive in nature, that affects the central nervous system. In MS, the immune system mistakenly attacks myelin (the fatty insulation around nerve fibers) causing damage to axons and leaving lesions (scarring) that interfere with the transmission of signals from the brain to the body.

While most individuals have a relapsing form of the condition, characterized by 'flare-ups' of disease activity and slow progression (worsening) over time, about ten percent have a chronically progressive form of the disease, in which the condition advances more quickly. 

Key Facts

• Sclerosis is a Greek word meaning "scars." The name 'multiple sclerosis' refers to the multiple sites of scarring (lesions) frequently found on the brain or spinal cord of an individual with MS.
• MS is not contagious.
• MS is not inherited or genetically transmitted, although there does seem to be some genetic susceptibility to the disease.
• MS is a progressive disease and, currently, there is no cure.
• MS rarely has a direct effect on a person's life span. The greater affect is on quality of life.
• Increased understanding of MS has led to the development of many new treatments that target both the disease process and its many symptoms.

Who:

• The disease can affect people of all ages, but the most common onset occurs between the ages of 20 and 40.
• Among young adults, MS is the most common disease of the central nervous system.
• MS affects women more frequently than men, estimated at a 3 to 1 ratio.
• MS can affect individuals of any ethnic group, though individuals of northern European ancestry appear to be at higher risk.
• Symptoms are typically worse at onset for African-Americans versus Caucasians, with greater involvement of the optic nerve. 
• Individuals with a first degree relative with MS have a slightly higher risk (2.5 percent) of developing the disease.  

What:

• Because MS can affect nerve signals to all areas of the body, there are more than 50 recognized symptoms.
• Common initial symptoms of MS include visual disturbances, numbness and tingling, balance and walking difficulties, fatigue and weakness.
• About 85 percent of people are initially diagnosed with the relapsing form of the disease. 
• Without disease-modifying therapy, about 50 percent of those diagnosed with relapsing MS will become progressive after 10 years.
• Without disease-modifying therapy, about one-third of those diagnosed with relapsing MS will be using a wheelchair after 20 years.

When: 

• The first official case of MS was recognized in 1868. 
• MRI was first used in the diagnosis of MS in 1981. Prior to this time, diagnosis could only be made by clinical history and neurological examination. 
• The first disease-modifying treatment for relapsing MS was approved by the U.S. Food and Drug Administration in 1993. 
• The first disease-modifying treatment for the progressive form of MS was granted "Breakthrough Therapy Designation" by the FDA in June of 2016, to expedite the review and approval process.

Where:

• An estimated 2,500,000 around the world have MS.
• In countries further from the equator, the incidence of MS increases.
• In the U.S., roughly 1 in 100 people have MS. 
• The rate of MS in northern U.S. states is twice that of southern states.

Why:

• The cause of MS is not entirely understood, but research suggests that the cause of MS is a combination of factors, possibly including genetics, environment, and diet, as well as viruses or infectious agents.
• In identical twins, if one twin has the condition, the other has only a thirty percent risk, indicating that the disease is not strictly genetic.
• Research on the cause of MS currently pursues many varied lines of inquiry, examining (among other things) the role of immune cells, the gut biome, vitamin D, and several genes. Each appears to provide pieces to the puzzle of MS.