Multiple sclerosis course labels are being outgrown by the biology they were meant to describe
For years, multiple sclerosis has been sorted into three broad clinical buckets: relapsing-remitting, secondary progressive, and primary progressive. Those labels remain familiar in clinic notes, trial protocols, and regulatory conversations. They also now look too blunt for the disease they attempt to capture.
A Roadmap from participants in an International Advisory Committee on Clinical Trials in Multiple Sclerosis workshop argues that the conventional course descriptors no longer reflect the full disease spectrum or the underlying biological mechanisms. The case for change is not cosmetic. It is driven by a growing mismatch between what neurologists observe at the bedside and what the disease is doing beneath the surface.
One sentence captures the central problem: patients can worsen without a clean relapse, and inflammatory activity can coexist with neurodegeneration long before disability accelerates.
Why the classic relapsing and progressive categories are losing precision
The traditional framework was built for a time when clinicians needed a workable language for a heterogeneous disease. It helped standardize communication, trial eligibility, and treatment discussions. Even so, those descriptors compress multiple biological processes into labels defined largely by outward clinical behavior. A person may appear to remain in a relapsing phase while silent injury continues, while another may be classified as progressive even though inflammatory activity still shapes the disease course.
That mismatch has become harder to ignore as newer work has described phenomena such as progression independent of relapse activity, silent progression, and spinal cord atrophy predicting progressive disease in relapsing multiple sclerosis. The references attached to the Roadmap point to a field that has already started moving beyond simple surface phenomenology. The disease course is increasingly viewed as dynamic, not static; layered, not linear.
In practical terms, the old labels can blur two different questions clinicians need answered at the same time: what is the patient experiencing now, and what biological process is driving the trajectory over time?
A biologically informed framework would separate mechanism from appearance
The Roadmap advances the idea that new course descriptors should be biologically informed rather than solely phenotype-based. That distinction matters because course labels shape treatment logic, trial design, and how progression is interpreted over long follow-up. If a label captures only relapse pattern, it may miss ongoing tissue injury. If it captures only disability accumulation, it may miss inflammatory activity that still requires treatment.
Biology-based classification would aim to track the processes most relevant to outcome: inflammatory activity, neurodegenerative change, and progression that occurs apart from overt relapse. A framework built on those axes would better reflect why disability can increase even when conventional relapse counts stay quiet. It would also align more closely with imaging and biomarker advances that increasingly reveal disease activity invisible to routine clinical observation.
The appeal is straightforward. A neurologist does not treat a label; the neurologist treats the process behind it.
Trial design, prognosis, and patient counseling all stand to change
Clinical trials in multiple sclerosis depend on course descriptors because they define who enters a study, which endpoints are emphasized, and how response is interpreted. If descriptors are too crude, trial populations become biologically mixed in ways that obscure treatment effects. A biologically richer framework could reduce that noise and help distinguish therapies aimed at suppressing relapses from those intended to slow progression itself.
The same issue reaches into prognosis. A patient’s disease course label often becomes shorthand for expected future disability, yet the references cited in the Roadmap reflect a field in which prognosis is no longer cleanly predicted by the old categories alone. Some relapsing patients accumulate disability quietly. Some progression is decoupled from relapses. Some measures of disease burden are only visible through long-term imaging or advanced analytic frameworks. The clinical vocabulary needs to catch up with that reality.
For patients, the stakes are personal as well as scientific. Labels influence how disease is explained, how hope is framed, and how future treatment options are discussed. When a descriptor fails to capture ongoing progression or inflammatory activity, counseling can become less precise than it should be.
Moving from a fixed label to a dynamic description of disease course
The Roadmap does not present a finished replacement system in the abstract, but it does propose a transition toward a more dynamic description of the multiple sclerosis disease course. That is an important signal in itself. Rather than swapping one rigid taxonomy for another, the field appears to be moving toward a model that can change as the disease changes.
Such a model would likely need to work across contexts of use. In the clinic, it would need to support communication and treatment decisions without becoming cumbersome. In trials, it would need enough structure to stratify participants and interpret outcomes consistently. In research, it would need to accommodate evolving concepts such as progression independent of relapse activity and the pathobiological foundations of progression.
The challenge is not merely technical. Any revised system must remain understandable to clinicians, useful for patients, and robust enough for regulatory and research use. It must also avoid trading one oversimplification for another.
The workshop message is clear even without a final taxonomy
What emerges from this Roadmap is less a final answer than a directional shift. The field is no longer satisfied with course descriptors that describe the visible shape of disease while ignoring the biology underneath. The language of relapsing-remitting and progressive disease still has value, but it may no longer be sufficient on its own.
The transition will likely be gradual because the old framework is deeply embedded in practice, literature, and trial history. Even so, the pressure to revise it is building from multiple directions: clinical observation, imaging, disability research, and the recognition that progression can unfold outside the boundaries of a relapse-based model.
For neurologists, the practical implication is not to abandon current terminology overnight. It is to recognize that these categories are increasingly being asked to do too much with too little biological resolution. The next generation of descriptors will need to say more about mechanism, not just chronology, if they are to remain clinically useful.
The remaining question is how quickly that mechanism-based language can be translated into day-to-day care, where patients still need a clear explanation of what their disease is doing now and what it is likely to do next.