It generally first occurs in people in their 20s or 30s. Its cause is unknown, but strong evidence suggests MS may result from an autoimmune process in which immune cells mistake myelin as a foreign invader and attack it. The disease does appear to run in families. As many as 20 percent of people with MS have at least one affected relative. MS doesn't always result in severe disability.
Many people actually have minimal neurological disability and live a normal life.
Early signs of MS may be subtle and non-specific. Blurred or double vision is often the first symptom. Other early symptoms may include localized tingling or numbness, hand or leg weakness, fatigue, dizziness and loss of coordination and balance. As the disease gradually progresses, muscle spasms, slurred speech, vision loss, problems with bladder, bowel or sexual function and paralysis may develop. Occasionally, mental changes such as forgetfulness or confusion occur.