What Is SMA?

Spinal Muscular Atrophy is more commonly known by the letters SMA. It is also sometimes referred to as autosomal recessive proximal spinal muscular atrophy but however you say it, it all means the same thing–that it is a rare neuromuscular disorder that affects many thousands of people throughout the world.

When life begins in the womb, all of us are given two sets of chromosomes. One from our mother, one from our father. This is our genetic code and if all goes well, we are born healthy. However, a lot can happen during gestation that affects pairs of chromosomes. Most of us are aware that having an extra copy of chromosome 21 for example leads to Down Syndrome. A mother and a father can both be carriers for spinal muscular atrophy and themselves would not be affected, but if both pass it via their chromosomes to their offspring, the baby has the disease. It is something that can occur along all races and in all the countries of the world; it does not discriminate.

So what is it? SMA is defined as a loss of motor neurons and it comes with progressive muscle wasting. What happens behind the scenes if you will is that there is a defect in the SMN1 gene which encodes SMN which is a protein necessary for the survival of the motor neurons. Proximal (arms and legs) and the lung muscles are usually the first to be affected by the disease with others following as it progresses. Some babies born with the disease are so weak that they die shortly after birth, others survive birth but have problems throughout their lives.

Areflexia which means below normal or absent reflexes, muscle weakness, poor muscle tone, loss of strength of respiratory muscles, weak cough, limpness, difficulty sucking and/or swallowing and poor feeding are all indicative of someone with spinal muscular atrophy. These people often have to use a wheelchair and have a lot of help doing things others take for granted. While their body may be weak, their brains usually are not, with most kids diagnosed with SMA being of above average intelligence.

Can this be cured? Well, there is some hope with a new drug that was approved by the FDA in December of 2016. It is called Nusinersen and it is taken by injection into the central nervous system. Clinical trials so far have been inspiring but there is still a wait time until the drug becomes widely available. With any luck, this is just what patients and children have been waiting for.