Spinal muscular atrophy, or SMA, is a group of genetic disorders that affects muscle movement. This happens due to a loss of nerve cells in the spinal cord and brainstem, which causes weakness and muscle wasting. SMA is both a type of motor neuron disease and a neurological condition. There are some types of SMA that can be fatal, while other types may have mild symptoms.

The various types of SMA, their symptoms, and prognosis include the following:
1. SMA1 Type

• Onset

The onset of this condition occurs within the first six months after birth.

• Symptoms

Muscle weakness is the main symptom and difficulty in moving the muscles become apparent. The child can never sit on its own. The floppy limbs give it the name “floppy baby syndrome.” The main problem with this type of SMA is difficulty with swallowing and breathing.

• Prognosis

The lifespan may be around two years for around 68% of patients. Moreover, the lifespan for around 82% of patients is around four years. However, proper respiratory care and treatment can help extend their lifespan.

One of the severe types of spinal muscular atrophy (SMA) is SMA 0 (which is a variant of SMA1). The babies affected face severe symptoms and breathing problems that can be fatal.

2. SMA2 Type

• Onset

The onset of this condition occurs between six to eighteen months of age.

• Symptoms

Muscle weakness is seen within the first few months. Weak muscle tone and difficulty with sitting and walking are the main symptoms. Difficulty with swallowing and breathing can be observed.

• Prognosis

A majority of children live up to early adulthood if given proper care and respiratory support. If good treatment is provided, they can live even until late adulthood.

3. SMA3 Type

• Onset

Symptoms in this type typically appear only after the child becomes 12 months of age. It may even appear at a later stage during early adulthood.

• Symptoms

While they face difficulty with walking, most of them would be able to walk independently. Running and going up and down the stairs could also be a problem they face. Their legs are weaker than their arms.

• Prognosis

Those having SMA3 can lead a normal life like everyone else. Wheelchair support may be needed in some cases, other than that they’re unlikely to face any major problems.

4. SMA4 Type

• Onset

This type is called late-onset or adult-onset. During childhood, symptoms are unlikely to be seen. Symptoms may gradually appear at around the age of 35.

• Symptoms

Muscles start to become weak gradually in this type. Tremors and twitching are common symptoms. The curvature of the spine is also seen (scoliosis). Symptoms rarely become severe. While they may find it difficult to walk normally, loss of movement is unlikely to occur. Some people may require a wheelchair to move around as they age.

• Prognosis

This is a very rare type of SMA and less likely to occur. Those suffering from this condition can expect to lead a normal life. After the age of 60, support for walking may be needed.

The types of spinal muscular atrophy, or SMA, the symptoms, and prognosis for each of the types of SMA outlined in this article aims to give more information about this genetic condition.