How do you distinguish between primary progressive MS versus relapsing remitting MS with superimposed relapses in a newly diagnosed patient that is naive to treatment?

Relapsing versus progressive MS are clinical phenotypes lacking clear objective radiologic or paraclinical distinctions. Recent literature emphasizes commonalities between these phenotypes, largely framing them as a spectrum of one disease rather than discrete disorders. Originally, these clinical phenotypes, as defined by Lublin et al, aimed to enhance harmonization for clinical trials (Lublin et al., PMID 24871874).

To address the specific question, it is often driven by a patient recall. For instance, a patient recalling a discrete clinical relapse (worsening function persisting for a period that later improved or persisted) without progression of disability (over at least one year) would be labeled as having relapsing-remitting (though i...

First, I scrutinize the history to look for evidence of progression over a year or more as we often determine PPMS retrospectively as it has a much more subtle presentation than RRMS. Patient specific factors such as presenting with a progressive myelopathy, male gender, age in 40s, primarily spinal cord disease with a paucity of brain involvement are helpful as well.

PPMS with superimposed relapses can be difficult to tease out, but it comes down to whether or not there has been progression from the onset of disease in the end.