What are the four types of multiple sclerosis?

The four types of multiple sclerosis, commonly referred to as MS, are relapsing-remitting MS, secondary-progressive MS, primary-progressive MS and progressive-relapsing MS, according to the National Multiple Sclerosis Society. Each form varies in level of severity from mild to severe.

Eighty-five percent of patients diagnosed with MS have the relapsing-remitting variation, or RRMS, states the National MS Society. People with RRMS have symptom flare-ups that alternate with periods of few or no symptoms. Most people with RRMS eventually develop secondary-progressive MS. SPMS progresses at a steadier pace.

In primary-progressive MS, neurological symptoms decline regularly right from the start of the disease. PPMS accounts for about 10 percent of MS patients. With progressive-relapsing MS, symptoms steadily worsen and flare up considerably at certain intervals.