You will have noticed that a lot of discussion on this blog has recently been devoted to the topic of secondary progression or smouldering MS or whatever else you want to call it. At the moment there is no standard terminology for describing the scenario of someone with MS who is NEDA-2 (no relapses and no activity on MRI) who is getting worse. The getting worse could be overt, i.e. worsening EDSS, or a more subtle deterioration, which can only be detected using more sensitive outcome measures, or asymptomatic.

Can you let us know which term you prefer?
- Non-relapsing SPMS
- Inactive SPMS
- Hidden SPMS
- Hidden progression
- Silent progression
- Progression independent of relapses (PIRA)
- Smouldering MS
- Worsening MS
- Festering MS
I personally don’t like the use of secondary progression in the term. This excludes MSers with a primary progressive course who have the same pathology and entrenches the dogma that relapse-onset MS and PPMS are different and separate diseases.
Hidden is another term that I don’t like; what is hidden for some MSers may not be hidden for other MSers. For example, cognitive impairment only becomes a problem when you stress your brain. Some MSers may be in a life stage when cognitive stressors are rare and others may stress or test their cognitive abilities on a daily basis.
The term PIRA seems to have the lead at the moment and is being used more and more in abstracts and meetings. Worsening MS is a catch-all phrase that by definition can occur in the presence or absence of relapses and hence according to the Lublin classification you can have active-worsening and inactive-worsening MS. Please note that according to Lublin the worsening has to be overt, i.e. captured using an objective outcome measure.
I like smouldering MS because it creates a visual analogy of what is happening to the brain and spinal cord of MSers. In other words, the flames or relapses and focal MRI activity have been quelled, but the embers continue to burn. It also implies that the embers can fire-up and reignite the flames at any stage. I have a potential conflict in that the term ‘smouldering MS’ may have been used first on this blog and hence we have a vested interest in this term being selected.
What do you think?
CoI: multiple
Thanks Gavin
I’ve been describing such patients as having smouldering MS for many years – but I prefer PIRA as a clearer statement of the issue/target population of PwMS.
I think PIRA works best at an academic level and smouldering better as an analogy to explain what is happening. At the moment PIRA is out in front.
Smouldering catches something about the sly, nasty side to the disease. When I got on Natalizumab when it first came out there was a great hope that it would stop the disease given the understanding at the time that the disease was caused by inflammation coming into the CNS. Of course, things weren’t as simply and the true nature of the disease is revealing itself.
Some 30 years ago we bought an old timber frame cottage. The walls were damp and the wall paper was peeling. My wife commented that all we needed was to dry the place out with a dehumidifier and then repaper. After stripping back the paper and pulling off most of the plaster we saw that the problem was much bigger. An expert confirmed it was wet rot which had eaten away most of the timbers. Remind me of MS – need a real fix rather than just papering over the cracks.
I can personally relate to your post, Siv – Beautifully captured! Thank you for putting into words what I have been unable to fully express.
I think smouldering MS is a great term and one I identify with but PIRA is very clear for communicating with government agencies and pharma
I agree, I love the description of smouldering but I really think PIRA is a nice clear concise term for non experts, government etc
I agree completely. I think it depends who you are talking to, a point that you make. I will also add that clinicians and academics would prefer PIRA cos it is a meaningless word but acronyms assume the speakers knows something special. To people with MS the term smouldering MS describes it perfectly. Suspect ProfG is looking for an acronym
I chose the term ‘smouldering’ because I agree with Prof G’s comments – but thinking it over I’m not so sure. Did I understand it wrong that because MS is by nature progressive, EVERYONE’S condition is smouldering, whether or not there are detectable changes? (I suppose unless they’ve had a complete re-boot to the immune system)
How would you describe someone that is SPMS for 15-20 years, but has a relapse 24 years after their last one?
I think PIRA would still cover this, although it is progressive independent of relapses, this doesn’t mean that relapses don’t ever occur, just that there is no correlation between relapses and progressions
Sorry, I voted PIRA but changed my mind to smouldering MS. I terms of the theory that relapses are not the real disease but a reaction to what’s going, smouldering MS makes more sense.
Hi Prof G, I like the term ‘smouldering’ as I think it describes the type of MS I have and it makes more sense as it really does feel like it’s smouldering away and now and then the flames ignite due to stress, worry, tiredness or exhaustion. The flames can really burn high especially when my brain is put under a lot of pressure. I can no longer fully multi-task in a stressful environment & those flames interrupt my thought process, so much so that I can’t think straight. The burning electrical shooting sensations feel are very real & catch you throughout the day, making you wonder if it is really you or your body has been replaced by an over-sensitive, battery needs charging or changing, stiff & in need of lubrication, ‘Robot!’ So smouldering is good but don’t forget to mention the ignited flames too – as they too are part of the smouldering MS.
Smouldering might not be easy to translate in non English languages (it doesn’t sound good in mine at least). PIRA or Silent Progression are more practical and easy to understand from non specialists.
Is it possible to title the paper PIRA but when first referencing PIRA in the paper, the alternative of ‘smouldering MS’ is mentioned during the explanation of what PIRA is? – I agree with other commenters that PIRA is more translatable and a good definition for non-MS (and even MS!) specialists, but that it’s also v important to explain what this means in the context of the disease, that it is ‘independent’ of whether someone is relapsing or not.
So kill 2 birds with 2 stone please 🙂
Don’t know if you can combine the two to smouldering progression independent of relapses: SPIRA.
I’d endorse the use of SPIRA. It’s very useful as it bridges the need to have progression despite being NEDA2 understood by PwMS and the requirements of clinicians, Govt etc.
I like SPIRA too.
Smouldering is a good factually description.
I think PIRA.
Smoldering some residual flames never go out. Short easy to understand for lay folks like me. God bless you and yours!
Hi Gavin
I prefer the name “silent MS” as in my mind it best describes. No signs of progression on mri etc but disease getting worse
Smouldering would leave a sign which this doesn’t
I would suggest:
Smouldering – Underlying progressive disease process
PIRA – Smouldering that has manifested itself in clinical worsening
I think SPIRA may be the best, as someone else suggested.
Maybe PrfG will explain PIRA it is quite complex
Smouldering MS is not perfect but I voted for it because it’s a suitable general term that describes the condition, and it’s an existing medical term for a similar stage of myeloma. Also reasonably precise. Search web ‘precision vs accuracy diagram’ for explanation. Smouldering for now anyway.
If this is one disease (and you say it a zilion times)
Why two responses?
https://medicalxpress.com/news/2019-07-differences-ms-patients-cerebrospinal-fluid.html
A metabolic perspective on CSF-mediated
neurodegeneration in multiple sclerosis
doi:10.1093/brain/awz201
I voted for smouldering. Why? Speaking as a marketer – several reasons
1) you need something that stands out from PPMS SPMS NEDA MRI etc. it’s a disease full of too many acronyms and if you want to shake the community on its head on more bloody acronym wont do a damn thing but fade into a cluttered background with all the rest.
2) The term “smouldering” carries a sense of urgency about it, that if you’re still “smouldering “ despite high efficacy DMD and “stable mri” then surely something must be done , and pronto!
3) Easily understandable by both hcps and pwMS (hey, I snuck two more acronyms in there!) and we sure do need more dialogue that both can understand
4) reinforces that this is ONE disease, that even with a “stable” mri you can have disease that damages the brain without better funding, treatment, research.
In most cancers a “smouldering “ tumor is treated as the urgent impending life threatening disaster it is. Same with MS yet the medical community does not seem to exhibit the same kind of urgency.
5) change the language, change the dialogue. Perception is everything.
My 5 cents and apologies for the colourful language! It’s what happens when you get us Americans all fired up…
Great question prof G.
So many different symptoms, for different MSers (apparently) and over time. With each patient unique and having their own perspectives, I can only comment from experience and the term “smouldering MS” is what resonates with me. Although my condition outwardly is trending “progressively” over time (although MRIs are stable), yet each day (and hours) can be different. One morning or afternoon I feel unexpectedly I can exercise and even run a marathon (ha ha – in my mind) and on others in spite of my best intentions I am fatigued and unable to proceed confidently without an aid, or to concentrate readily.
I love the allusion of smouldering MS and use it as it makes so much sense but I suspect PIRA will work better for the medical and scientific community.