Progressive-relapsing multiple sclerosis (PRMS) is the least common form of multiple sclerosis (MS). Progressive-relapsing MS accounts for about 5 percent of all types of MS and is now considered to be part of primary-progressive MS (PPMS), instead of its own MS subtype. In general, MS is an autoimmune disease in which the body’s immune system attacks its own nerves and brain cells. This central nervous system disease process destroys the protective coverings of nerves, known as the myelin sheath. These myelin sheaths are important in the process of how nerves throughout the body communicate with one another.

The disease course of progressive-relapsing MS is characterized by a gradual worsening of the condition from the very beginning, similar to PPMS. However, unlike PPMS, occasional symptom flare-ups (relapses or exacerbations) are similar to those experienced by people with relapsing-remitting MS (RRMS). In most cases, the symptoms of the disease and disability of the PRMS subtype are similar to PPMS. In fact, after the meeting of the International Advisory Committee on Clinical Trials of MS in 2013, the definitions for diagnosis changed. It was decided that people previously diagnosed with PRMS would now be considered to have PPMS: active (at the time of relapses or new brain lesions) or not active but with progression.

What Is Progressive-Relapsing MS?

Primary-relapsing MS used to be considered a rare form of PPMS. Because these two subtypes of MS are so similar, PRMS is now considered a subtype of PPMS that is either in an active or not active state. In addition, because it is so rare, there is little information regarding the clinical symptoms and disease course specific to the PRMS subtype.

It was originally thought that relapses were rare in cases of PRMS. But one small study showed that relapses are more common for this subtype than was once thought. This same study also showed that disability may accumulate more rapidly in individuals with PRMS than in those with the regular form of PPMS. Although this research only included a very small number of participants, the results nevertheless may provide some insight into the disease.

Causes of PRMS

The causes of this form of MS are largely unknown. In general, multiple sclerosis has been linked to:

• Abnormal immune responses (overactive T cells and B cells)
• Genetics (hundreds of genes, many related to immune factors)
• Environment (low vitamin D levels, geographical location, smoking, obesity)
• Ebstein-Barr virus exposure

Signs and Symptoms of PRMS

The symptoms of PRMS are similar to those of PPMS. The main symptom of both forms is a gradual worsening of disability. Sometimes, PRMS involves relapses or a return to an active state. Symptoms include:

• Fatigue
• Numbness or tingling
• Vision problems (double vision)
• Spasticity or stiffness of the muscles
• Difficulty controlling the bladder or bowels
• Problems with thinking and memory
• Difficulty with walking and coordination
• Muscle weakness
• Paralysis
• Dizziness or shakiness
• Mood changes (depression)
• Sexual dysfunction

Diagnosis of PRMS

PRMS is no longer thought of as its own disease. To diagnose PRMS, a doctor would have to decide if the individual with MS-associated symptoms meets PPMS diagnostic criteria but with the occasional presence of relapses. Then, if relapses are present, individuals would be classified as either PPMS active or PPMS not active.

The McDonald Criteria must be met for PPMS. This includes at least one year of disease progression and two out of three of the following:

• More than one brain lesion characteristic of MS
• More than two spinal cord lesions
• Presence of oligoclonal bands in a spinal fluid sample

PPMS is hard to diagnose because it can look different from other forms of MS during a brain scan, such as magnetic resonance imaging (MRI). Because PRMS is essentially a form of PPMS, diagnosis can be even more difficult.

Treatment of PRMS

There is no one standard medical treatment for PPMS or PRMS. During the time of a relapse, steroids are typically given to help alleviate new symptoms. There are other therapies available to decrease the frequency of relapses, namely a group of medications known as interferon beta. Some treatments may be effective for PPMS, such as:

• Immunomodulatory drugs (such as ocrelizumab)
• Epstein-Barr virus-specific T-cell therapy

Whether these approaches are also therapeutic in cases of PRMS is not quite clear. Because PRMS is so rare, and because it is now diagnosed as a component of PPMS, it has not been studied thoroughly. Therefore, the best course of treatment is largely unknown.

Prognosis and Outlook of PRMS

Compared with RRMS, people with PPMS have a poor prognostic outlook. One study found that PPMS and PRMS were incredibly similar in both their clinical symptoms and general prognosis. In this study, researchers observed that PRMS started at an earlier age than PPMS. The similarities between these two types of MS likely played a major role in PRMS merging into the PPMS disease entity.

Researchers must continue to study MS in its many forms to understand the nature of this complicated disease. Once more research is available, neurologists will be able to identify better and more efficient treatment options.

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