Spinal muscular atrophy (SMA) is a rare, genetically inherited neuromuscular condition that causes progressive muscle weakness and loss of movement as a result of muscle wasting (atrophy). There are now three therapies that people with SMA can access in the UK: nusinersen (also known as Spinraza), risdiplam (also known as Evrysdi), and a gene therapy called Zolgensma.
Muscles are controlled by nerves to make them move. The nerves that stimulate muscle, together with the muscle fibres to which they are attached, form something called a motor unit. The enlargement of these motor units is an important part of the disease process in people with SMA. Enlarged motor units are thought to experience more oxidative stress (an imbalance in oxygen-containing molecules, which causes harm to cells), which has a negative impact on their survival.
