Spinal muscular atrophy (SMA) is a genetic condition that can affect adults and even children. It also affects the ability of a person to control muscular movements. There are different types of spinal muscular atrophy each of which is different from the other. SMA or spinal muscular atrophy is a genetic condition that affects children and in some cases even adults. The disease leads to the voluntary muscles becoming weak or breaking down.

As a result, controlling muscular movements becomes difficult. It can lead to problems in movement, problems while swallowing, and can also cause death. The main cause of SMA is attributed to a gene mutation wherein a protein known as SMN (Survival of Motor Neuron) is deficient or absent. There are four main types of spinal muscular atrophy (SMA). The classification of the types is based on its onset, i.e., when this genetic condition develops. The four types include the following:

1. SMA1 (Infantile)
SMA1 is known as infantile-onset spinal muscular atrophy. Here, the onset of the disease happens from birth to six months of age. It’s also referred to as Werdnig–Hoffman disease. The disease becomes apparent immediately at birth or within six months. Limbs that are floppy in nature and weak movement of the trunk are some of the characteristic symptoms. These infants find it very difficult to move. Holding their head up, swallowing, and even breathing becomes very difficult.

2. SMA2 (Intermediate)
This intermediate type of the disease is also called Dubowitz disease. It usually occurs after the child crosses six months of age. The condition can develop anytime until the age of 18 months. In most cases, it affects the lower limbs and the children affected with this condition are unable to stand. They can also suffer from breathing problems. They can survive into adulthood with proper treatment and care.

3. SMA3 (Juvenile)
This is a juvenile form of the disease that is known as Kugelberg–Welander disease. The disease becomes apparent after the child crosses one year of age. This is a relatively mild form of SMA. These children may be able to both stand and walk. However, they may face a lot of difficulty in getting up from a sitting position. Most juveniles suffering from SMA3 can expect to lead a normal life with a higher risk of developing respiratory problems

4. SMA4 (Adult onset)
This is a very rare form of the disease that becomes apparent after the age of thirty. The muscles gradually become weak and walking becomes very difficult. Apart from difficulties in walking, weakness in limbs, and occasional twitching of limbs, there are no other symptoms. They can lead a normal life but may need wheelchair assistance.

The types of spinal muscular atrophy (SMA) presented in this article would have helped one get an overview of this genetic condition and understand how it manifests itself.