Key takeaways
- ~1,000 UK SMA patients actively registered across the four regional NHS SMA networks (Manchester, GOSH/Evelina, Birmingham/Alder Hey, Edinburgh) · SMA UK patient organisation census 2023
- 1,800-2,000 total UK SMA prevalence estimate including the pre-newborn-screening-era legacy population outside active network registers · NICE HST15/TA755/TA588 population framing
- 15% / 40-45% / 40-45% estimated UK therapy share split: Zolgensma / risdiplam / nusinersen · NHS England SMA commissioning policy 2023
Two UK SMA counts disagree by design: roughly 1,000 actively-monitored NHS-network patients against 1,800-2,000 in total prevalence, and the gap is the pre-newborn-screening legacy population.
Two independent methods size the UK SMA population, and they disagree for a specific, sourced reason. The network-census method counts patients actively registered across the UK's four regional NHS SMA networks (Manchester, GOSH/Evelina, Birmingham/Alder Hey, and Edinburgh): roughly 1,000 patients, split Type 1 approximately 200, Type 2 approximately 400, Type 3 approximately 350, and Type 4 approximately 50. The prevalence method starts from a broader population base and arrives at 1,800-2,000 total UK SMA patients across every type and age. Triangulating the two does not mean picking one; it means identifying what the 800-1,000-patient gap actually represents.
That gap is the pre-newborn-screening-era population: patients diagnosed before national SMA newborn screening began in 2021 and before the four current regional networks consolidated case ascertainment, some of whom are older Type 2/3 or undiagnosed Type 4 adults managed outside the specialist network's active registers, in general neurology or historic paediatric follow-up rather than the current SMA-specific commissioning pathway. This is the same registry-versus-epidemiology triangulation this model applies across every geography: a narrower, actively-tracked cohort and a broader total-prevalence estimate are not in conflict, they are answering different questions, and the gap between them, roughly 800-1,000 patients, is precisely the addressable legacy population that has not yet been swept into active NHS SMA network follow-up. Layered onto whichever total a client model adopts, therapy share splits roughly as follows: Zolgensma approximately 15% (Type 1 and newborn-screening-identified infants), risdiplam approximately 40-45%, and nusinersen approximately 40-45%, a split driven by oral-administration preference in paediatric patients and established use in older adults.
UK SMA sizing — NHS network census versus total prevalence estimate
| Sizing Method | Population Estimate | Source |
|---|---|---|
| Registry-based (four-network NHS census) | ~1,000 patients, Types 1-4 | SMA UK patient organisation census 2023 |
| Epidemiology-based (total prevalence) | 1,800-2,000 patients, all types/ages | NICE HST15/TA755/TA588 population framing |
| Estimated legacy-population gap | 800-1,000 patients | Derived from network-census vs prevalence-estimate gap |
| Therapy share split | Zolgensma ~15%; risdiplam ~40-45%; nusinersen ~40-45% | NHS England SMA commissioning policy 2023 |
Sources: SMA UK patient organisation census 2023; NICE HST15, TA755, and TA588 evidence submissions; NHS England SMA commissioning policy 2023.
What this model answers
Every section answers a named commercial question your team is asking, scoped to your asset.
- Why do the ~1,000-patient NHS network census and the 1,800-2,000 total prevalence estimate disagree, and which should a launch model use? • Network-census methodology and its four-region scope • the broader prevalence estimate's basis • the specific 800-1,000-patient gap and what it represents
- Who makes up the gap between the actively-tracked cohort and total prevalence, and how would a new entrant identify them? • Pre-newborn-screening-era legacy population characterisation • undiagnosed Type 4 and older Type 2/3 patients outside active network follow-up • identification-pathway options
- How does therapy share split across Zolgensma, risdiplam, and nusinersen once a total population is chosen, and what does that mean for a fourth entrant's addressable base? • Type-and-age-based share modelling (15%/40-45%/40-45%) • sensitivity to which total-population figure is adopted • addressable-base sizing for a new entrant
What's inside
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1 · The Binding Constraint 2 pp
- Why the ~1,000-patient network census and the 1,800-2,000 total prevalence estimate are not in conflict
- Pressure-tested against the pre-NBS legacy-population gap before the rest of the model is built out
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2 · Epidemiology-Based Sizing 3 pp
- The 1,800-2,000 total UK prevalence estimate and its basis
- How this compares to the global 1:10,000 incidence rate
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3 · Registry-Based Sizing — The Four-Network NHS Census 3 pp
- The ~1,000-patient census across Manchester, GOSH/Evelina, Birmingham/Alder Hey, and Edinburgh
- Type 1-4 split within the actively-tracked cohort
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4 · Triangulation & the Legacy-Population Gap 3 pp
- Why the 800-1,000-patient gap is the pre-newborn-screening-era population, not a measurement error
- Where this population sits relative to NHS SMA commissioning pathways
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5 · Sensitivity Analysis 3 pp
- Legacy-population identification rate ranked against prevalence rate as the binding assumption
- Scenario ranges tied to therapy-share splits by type
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6 · Editable Excel Model —
- The full triangulated model, re-runnable with your own assumptions
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7 · Client Alignment Questions 2 pp
- The open sizing questions your team must close before the number is used in planning
Appendix and source ledger included · 45-minute analyst readout included with delivery
Custom model delivered in 72 hours.
Assess this reportIncluded with every brief
Get Started
Commission this model
AXLRx delivers rare disease market sizing models built for forecasting and strategy teams sizing the UK SMA opportunity, including the pre-newborn-screening legacy population. Custom model in 72 hours.
- 1. Submit your requestSpecify your indication, market, and cohort definition.
- 2. Scoping callAXLRx analyst confirms triangulation methods and comparator set before building.
- 3. DeliveryResearch-verified sizing model in 72 hours with optional analyst readout.
How AXLRx builds this model
Prepared by MoatRx analysts on the AXLRx commercial consulting engine.
Every AXLRx market sizing model triangulates at least two independent methods, epidemiology-based and registry/census-based, before accepting a patient count. This is explicitly a sizing model (static patient count), distinct from a Patient Flow or forecasting model (dynamic revenue/uptake).
SMA UK sizing sources: SMA UK patient organisation census 2023, NICE HST15/TA755/TA588 evidence submissions for total-population framing, and NHS England SMA commissioning policy 2023 for therapy-share data.
- Four-network NHS census count and Type 1-4 split verified against SMA UK patient organisation census 2023
- Total UK prevalence estimate (1,800-2,000) verified against NICE HST15, TA755, and TA588 evidence submissions
- Therapy share split verified against NHS England SMA commissioning policy 2023
Frequently asked questions
Methodology Why do different AXLRx SMA UK reports cite ~1,000 patients in one place and 1,800-2,000 in another?
Both figures are correct for what they measure. Roughly 1,000 is the active caseload across the UK's four regional NHS SMA networks; 1,800-2,000 is the broader total prevalence estimate, including the pre-newborn-screening-era legacy population not consistently captured in current network registers. This model treats the gap between them as the addressable legacy population, not a data conflict.
Deliverables What formats are included with every model?
Every commissioned Market Sizing Model includes an editable 5-sheet Excel model (Cover, Model, Research Validation, QC, Sensitivity) and a PDF methodology brief, no PowerPoint deck, since a sizing model is built to be worked in directly, not presented from. An optional 45-minute analyst readout call is included.
Sources How is the patient count verified?
AXLRx triangulates every sizing estimate across at least two independent methods, registry-based and epidemiology-based; no single-source number ships unverified.