Spinal Muscular Atrophy (SMA) factsheets

The four main types of SMA vary greatly in severity and the effects vary between individuals:

  • SMA Type 1. Symptoms appear within the first few months of life, sometimes before birth. Children are never able to sit unaided and rarely survive their second birthday.
  • SMA Type 2. Symptoms usually appear between 7-18 months of age. Children are never able to stand unaided. Although the condition may shorten life-expectancy, improvements in care standards mean that the majority of people can live long and fulfilling lives.
  • SMA Type 3. Symptoms appear after 18 months of age. Children are able to stand and walk, but will become less able to walk over time. Life-expectancy is normal and most people can live long independent lives.
  • SMA Type 4 (also known as Adult Onset SMA). Symptoms appear in adulthood. It is not a life-threatening condition.

Our thanks to Spinal Muscular Atrophy Support UK (SMA Support UK), a certified member of The Information Standard, who have produced these factsheets. Muscular Dystrophy UK works closely with SMA Support UK and endorses the information provided in the above factsheets.

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