Spinal muscular atrophy (SMA) is a genetic condition that affects areas of the nervous system that controls voluntary muscle movement. It is caused by a lack of nerve cells, called motor neurons and the muscles progressively weaken. SMA affects 1 in every 10,000 births and the younger the age of onset, the greater the impact on motor function. The scale used to describe the level of functionality is from Type-0 to Type-4.
There is no cure for SMA currently, but there are treatments available that can help with symptoms. Types of SMA are as follows:
1. Type-0 SMA
This is the most severe form and it becomes evident in the womb. They will display reduced fetal movement and tend to be born with joint deformities. Babies born with type 0 have serious respiratory issues and usually do not live past infancy.
2. Type 1 or Werdnig-Hoffmann disease
This type of SMA is also very severe and is the most common. Between 50% and 70% of all cases of SMA are type 1. Symptoms will become evident normally before 6 months of age. Babies with Werdnig-Hoffmann Disease cannot hold their heads up on their own and also may have breathing issues. They will experience a weakening of the muscles and may experience trouble swallowing. Curvature of the spine is also common. Without treatment, life expectancy is reduced, usually up to the age of two. With proper treatment, kids with SMA can learn to sit and walk on their own.
3. Type 2 or Kugelberg-Welander syndrome
This is an intermediate form of SMA. Children with type 2 can walk, but experience muscle weakness and can become wheelchair-bound later in life. Also, breathing problems will play a factor in their quality of life. Many kids with type 2 SMA also risk developing scoliosis down the road. With early intervention, life expectancy can run into early adulthood.
4. Type 3 mild or juvenile SMA
Patients with type 3 SMA may not show signs until well into childhood where they may have trouble walking up and down stairs or running. Patients with juvenile SMA may be more susceptible to respiratory infections. They will experience muscle weakness. Usually type 3 patients have a near-normal life expectancy.
5. Type 4 or adult SMA
Patients with type 4 SMA will experience onset of the disease in adulthood. This is the rarest form of SMA. Patients can experience muscle tremors or twitching and scoliosis is another possibility, although the symptoms are usually mild. Treatment is very beneficial and can help to slow down the affects.