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The ‘Natural History’ of SMA

Before drug treatments (also sometimes known as ‘disease-modifying’ treatments) started to be developed and tested for 5q SMA, clinicians and researchers gathered information about what impact someone might expect the condition to have on them.

This is called the ‘natural history’ of the condition.

This has led to 5q SMA being divided into four main ‘Types’ of SMA: Types 1, 2, 3, and 4. Sometimes a baby is affected before birth; this is called Type 0.

These ‘Types’ of SMA were based on the age that symptoms began, and what physical milestones (e.g. sitting, standing, walking) could be achieved. It was agreed that there could be variation both within and between Types.

This classification system is still used for adults, teenagers and children living with SMA in the UK even though for many, care and treatment is changing the outcome of their SMA.


What would the ‘natural history’ be like for my child / me without drug treatment and care?

If your baby has been diagnosed with SMA, this may be because of their symptoms or because they have been part of the Oxford / Thames Valley-based SMA newborn screening study and been diagnosed with SMA. 

To try to answer this, a specialist clinician will examine any child or adult with suspected SMA.

They will also consider:

  • the age of the child or adult when the SMN1 gene deletion test confirmed SMA
  • any symptoms of SMA and when these first started
  • how many SMN2 gene copies the test result showed
  • any family history of SMA

And will refer to this summary:

Table adapted from Tillmann et al.

Your clinician will advise you what ‘natural history’ they would expect your child’s SMA to follow if they do not have drug treatment. They will also advise you of the latest clinical trial and real-world evidence for these drug treatments and what you might expect if your child is treated.

The links below describe, in general terms, the ‘natural history’ of the different Types of 5q SMA:
Image shows a little boy who has SMA Type 1 sitting in his Wizzybug wheelchair. He is next to his mum who is crouching down with her arm round him.

Symptoms & Effects of 5q Spinal Muscular Atrophy – Type 1

Image shows a young boy who has SMA Type 2, sitting in his Bugzi wheelchair.

Symptoms & Effects of 5q Spinal Muscular Atrophy – Type 2

Image shows a young adult who has SMA, standing and holding a drink in one hand. She is wearing a blue dress and white trainers.

Symptoms & Effects of 5q Spinal Muscular Atrophy – Type 3

Image shows adult man who has adult onset SMA, standing with his wife.

Symptoms & Effects of 5q Spinal Muscular Atrophy – Type 4