Causes of Primary-Progressive Multiple Sclerosis (PPMS)
The exact cause of MS is unknown, but doctors have suggested two different theories. One is that MS begins as an inflammatory process of the autoimmune system that causes loss of myelin. The second is that the disease may be an immune response triggered by a viral infection. This can later cause nerve degeneration or damage.

Research into what may trigger the immune system response responsible for MS is ongoing. Possibilities include viruses or environmental toxins. Why some people develop PPMS is also unknown. MS in any form isn’t contagious.

Who gets PPMS?
MS is more common in Caucasians than in other ethnic groups. Although relapsing forms of MS are more common in women than in men, both sexes get PPMS at about the same rate. PPMS tends to occur about 10 years later in life than the relapsing forms of MS.