What is primary progressive multiple sclerosis?

Multiple sclerosis (MS) is a disorder of the central nervous system that affects about 400,000 people in the United States. Most people with MS have relapsing symptoms and experience episodes lasting days or weeks of symptoms, such as:

  • numbness or tingling
  • weakness of a leg or arm
  • unsteadiness
  • bladder difficulty
  • visual symptoms

About one in ten people with MS do not have a relapsing course of the disease. These patients tend to have symptoms that gradually progress without typical relapses. Patients with the gradually worsening disease are considered to have primary progressive multiple sclerosis or PPMS.

What causes primary progressive multiple sclerosis?

Just as with multiple sclerosis in general, the cause of PPMS is not known. It is thought that the disease occurs in people who are susceptible to it due to some kind of genetic tendency. It is believed by some to be caused by a trigger, perhaps a virus. However, no specific cause for PPMS is known. PPMS, however, is not infectious.

What other diseases can mimic primary progressive multiple sclerosis?

There are other diseases that can look like PPMS and need to be considered. For example, some people inherit a tendency for stiffness and weakness in the legs; a family history may be helpful. Some people with low vitamin B12 levels may develop numbness and stiffness in the legs and will show changes in their MRI scans. Occasionally, Lyme disease may look like MS. Some people with viral infections such as HTLV-1 may have a spinal cord syndrome. Sometimes discs or spinal arthritis may compress the spinal cord, or a tumor may be pushing on the spinal cord. Other diagnoses should be considered when the diagnosis of PPMS is being made.

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