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Spinal Muscular Atrophy (SMA)

Hereditary disease that progressively destroys motor neurons

What is Spinal Muscular Atrophy? 

Spinal muscular atrophy (SMA) is a group of rare, progressive, genetic neuromuscular diseases, which can be fatal. The most common form is caused by the mutation or deletion of the ‘survival of motor neuron’ (SMN1) gene, which leads to a deficiency of SMN protein.1 This protein is found throughout the body and is essential to the function of nerves that control muscles and movement. Without it, nerve cells cannot function properly, leading to progressive muscle weakness and muscle wasting; and physical strength and the ability to walk, swallow or breathe can be significantly diminished or lost over time.1

Spinal muscular atrophy is the leading genetic cause of infant mortality. However, there is a wide spectrum of how severely the different forms of spinal muscular atrophy affect children and adults.1

How common is Spinal Muscular Atrophy?  

Approximately 1 in every 11,000 babies globally have spinal muscular atrophy.2,3,4 Males and females are equally likely to have this disease.

How is PTC Working to Treat Spinal Muscular Atrophy? 

The first at-home, oral treatment for spinal muscular atrophy in adults and children two months and older was based on PTC’s innovative splicing platform technology. The SMA program is a joint collaboration between PTC, the SMA Foundation, and Roche. Evrysdi™ (risdiplam) has been approved in nearly 100 countries, including the US, the European Union and Japan. Evrysdi targets and encourages the SMN2 ‘back-up’ gene to produce a greater amount of functional SMN protein.


[1] National Institute of Neurological Disorders and Stroke. Accessed December 2021.

[2] Verhaart IEC et al. (2017) Prevalence, incidence and carrier frequency of 5q–linked spinal muscular atrophy – a literature review. Orphanet J Rare Dis 12: 124.

[3] Verhaart IEC, et al. (2017) A multi-source approach to determine SMA incidence and research ready population. J Neurol 264: 1465-1473

[4] Sugarman EA, et al. Eur J Hum Genet. 2012;20(1):27-32.​

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