Overview Spinal muscular atrophy (SMA)

Spinal Muscular Atrophy (SMA) is a rare, genetically inherited neuromuscular condition.

It causes progressive muscle weakness and loss of movement due to muscle wasting (atrophy). This may affect crawling and walking ability, arm, hand, head and neck movement, breathing and swallowing.

There are different forms of SMA and a wide spectrum of how severely children, young people and adults are affected. The most common form of SMA is known as ‘5q SMA’ due to its genetic cause. 5q SMA includes the different ‘types’ or clinical classifications – Types 1, 2, 3 and 4.

How many people are affected by SMA?

Approximately 1 in 40 people carry the faulty SMN1 gene11 - that means there are around 1.6 million carriers in the UK. The incidence is the number of new cases of a condition or disease at any one time.

Recent studies indicate that approximately one in every 10,000 babies worldwide are born with a Type of SMA, and that Type 1 SMA accounts for approximately 60% of cases11,12 . In the UK in 2017, there were 755,043 live births13-15. This suggests that in that year approximately 76 babies were born with a type of 5q SMA.

The prevalence is how many people are living with a condition or disease in a population at any one time. Recent studies suggest between 1 and 2 people in every 100,000 worldwide have a type of SMA11,12 .


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