Spinal muscular atrophy is a neuromuscular condition that affects the muscles by weakening them. This medical condition is hereditary.
Below you’ll find an overview of this condition and its symptoms, causes, types, and treatment of this medical condition.
Spinal Muscular Atrophy (SMA): Symptoms, Causes Types & Treatments
Causes Of SMA
Spinal muscular atrophy is a medical condition that gets passed down to people from their parents. When the infant/child has this medical condition, it means that they have either two broken SMN1 genes that they inherited from each parent or their genes have mutated.
A healthy SMN1 gene produces what is known as SMN protein which the motor neurons need to function and survive. And an incomplete SMN1 gene has trouble producing SMN proteins, causing the motor neurons to weaken and, eventually, die.
Aside from SMN1 genes, we also produce SMN2 genes, which also produce SMN proteins but are smaller. Usually, we have 8 SMN2 genes, but having more than that causes more SMN protein production, thus resulting in less severe spinal muscular atrophy symptoms.
Types Of Spinal Muscular Atrophy
This type of spinal muscular atrophy is the rarest yet most severe, and it develops while the child is still in the mother’s womb. Babies with this type of SMA have joint problems and weak muscles for breathing and often do not survive.
Type 1 SMA is also severe, and infants with this condition have difficulty breathing and sucking. They also have difficulty holding up their heads or sitting. Infants with type 1 SMA often do not last longer than the age of 2.
Type 2 SMA is not as severe as the first two types, as children who have this condition often survive into adulthood. Children with this condition have weaker legs, making it difficult to sit, stand, and walk.
Unlike the previous types, which symptoms appear young in life, symptoms of this condition usually appear between the ages 2-17 years old. Having type 3 SMA allows you to stand and walk without help, but it is challenging to run, climb stairs, and get up the chair.
Type 4 SMA occurs during adulthood. It is the stage wherein you will experience muscle weakness, twitching, and breathing problems.
Symptoms Of SMA
Symptoms of SMA differ in each type. However, it usually involves the loss of muscle control over time. It will affect movements and cause increasing weakness. Most often it’s the muscles in the neck and torso that are impacted the most by this condition.
Treatment For Spinal Muscular Atrophy
Unfortunately, there is no cure currently for SMA.
Those who have this condition can get some benefits from therapy (both physical and occupational). They also will often require the use of crutches, walkers and wheelchairs. Orthopedic braces may also be helpful.
There are some drug therapies that can help as well.
One used in patients from ages 2-12 is Nusinersen (Spinraza®). This drug is injected near the spinal canal and stimulates the production of SMN protein. For adults, an oral medication, risdaplam (Evrysdi®) can help.
Another therapy is a gene replacement therapy for ages below two years old. This treatment includes a one-time IV infusion of a drug called onasemnogene abeparvovec-xioi (Zolgensma®). The way this drug works is by having a functioning gene replace missing/faulty SMN1 gene.