Spinal muscular atrophy (SMA) is a rare genetic disease. The most common type of SMA is caused due to insufficient production of a protein known as survival motor neuron (SMN). Without the adequate SMN protein, the body’s voluntary muscles begin to weaken, affecting movements like walking, swallowing, crawling, etc. This article details the stages and symptoms of spinal muscular atrophy so you can know more about this possibly-fatal condition.

Stages of SMA

There are four stages of SMA, each having variations in symptoms and the point in one’s life when the signs manifest.

1. Type 1

Also known as Werdnig-Hoffman disease, this is a more severe type of SMA and the most common one. It usually shows up at birth or within the first few months. Symptoms include loose limbs, weak movement, and a limited ability to move around. Affected individuals also find it hard to swallow, breathe, or hold their head up high. This type of SMA progresses rapidly, causing degeneration of muscles that can cause frequent respiratory issues and death of infants by the time they are 2 years old. Infants with type 1 SMA are never able to sit upright by themselves without support.

2. Type 2 

This type of SMA occurs between the ages of 7–18 months. The rate of progression may vary from child to child. The disease also affects their legs more than their arms. Children with SMA type 2 are unable to stand without any support. They are also more susceptible to respiratory infections. In some cases, children can reach adulthood, even with the disease.

3. Type 3 

The symptoms first appear anytime between 1 ½ years and puberty. An individual with type 3 SMA is able to stand and walk but struggles to get up from their seated position. They may also have to deal with muscle weakness and an increased risk of respiratory problems. Patients with type 3 SMA have a regular life expectancy.

3. Type 4

Symptoms for this type of SMA do not usually occur until the 20s or 30s. The patients who have type 4 SMA can walk during their adulthood but experience muscle weakness with age.

Symptoms of SMA

Now that the stages of SMA have been covered, it is vital to know the symptoms according to which it gets classified. The symptoms of SMA depend upon the severity, type, and age when the condition develops. Some of the common ones are as follows:

1. Difficulty in breathing
Children suffering from SMA do not have the muscle strength required to cough properly when required. As a result, the secretions stay inside the lungs, compromising their breathing.

2. Difficulty in standing
The condition causes muscle wasting and weakness that makes it difficult for the person to stand or walk. This symptom of SMA is seen in the first three stages, and eventually in the fourth stage.

3. Muscle weakness
Lack of SMN1 protein leads to muscle weakness and loss of muscle tone that can cause breathing and feeding problems. If you notice that your infant struggles to breathe or even sit, then be sure to discuss it with their doctor.

SMA is a degenerative condition that tends to get worse over time. Therefore, knowing about the stages and symptoms of spinal muscular atrophy can help you seek timely treatment for your loved ones.