Multiple sclerosis (MS) is classified into four types, characterized by the disease's progression.
- Relapsing-remitting MS (RRMS). RRMS is characterized by relapse (attacks of symptom flare-ups) followed by remission (periods of recovery). Symptoms may vary from mild to severe, and relapses and remissions may last for days or months. More than 80 percent of people who have MS begin with relapsing-remitting cycles.
- Secondary-progressive MS (SPMS). SPMS often develops in people who have relapsing-remitting MS. In SPMS, relapses and partial recoveries occur, but the disability doesn't fade away between cycles. Instead, it progressively worsens until a steady progression of disability replaces the cycles of attacks.
- Primary-progressive MS (PPMS). PPMS progresses slowly and steadily from its onset. There are no periods of remission and symptoms generally do not decrease in intensity. About 15 percent of people who have MS have PPMS.
- Progressive-relapsing MS (PRMS). In this relatively rare type of MS, people experience both steadily worsening symptoms and attacks during periods of remission.