About Spinal Muscular Atrophy
What is SMA?
Spinal Muscular Atrophy (SMA) is a devastating, often fatal, muscular wasting condition that affects thousands of people in the UK, of all ages, race and background. 1 in 40 of us carries the gene that causes SMA (around 1.5 million people in the UK). The prevalence of SMA is second only to cystic fibrosis.
There are three types of SMA that affect children:
- Type I is the most common form and is the severest type. Onset typically occurs before 6 months of age. Weakness is severe and manifests in difficulties moving, eating, swallowing and breathing. A child with Type 1 is lucky to reach their 2nd birthday.
- Type II is less severe. Onset typically occurs between 6 and 18 months of age. These children are able to sit at some point in their lives but never achieve the ability to walk. The most significant weaknesses are manifest in their proximal muscles. Respiratory health is a concern and should be monitored to avoid dangerous respiratory failure and chest infections.
- Type III is the mildest of the three types. Babies appear normal at birth, and diagnosis is generally made when they are over the age of two. Children with Type III range from those able to take a few steps to those who can ambulate throughout their home and community. As some children grow, their larger bodies and heavier weight make walking and other activities more difficult. A child may require a wheelchair to navigate their environment.
What causes SMA?
Spinal Muscular Atrophy is caused by the lack of a protein called 'survival of motor neuron 1' (SMN).
This protein is essential for the survival of the motor neurons - the nerves which control the movement of muscles. People lack SMN protein if they have two faulty copies of the SMN1 gene, which contains the instructions for its production. Without motor neurons, muscles cannot be controlled and wither away.
Progressive loss of motor neurons in the spinal cord causes muscle atrophy Muscular atrophy of the trunk can lead to skeletal deformities. Muscular atrophy of the breathing muscles can lead to fatal respiratory problems. Muscular atrophy of the swallowing muscles can lead to difficulties eating and swallowing.
How many people have SMA?
In the UK at any one time, between 5,500 and 6,000 people have SMA.
What is being done?
Rapid advances have been made since the SMN1 gene was first identified. Treatment pathways are under scrutiny:
- Mouse and fruit fly models have been developed which provide the means for high throughput screening. High throughput screening is a means of testing many thousands of possible treatment compounds using robotics and computers. This electronic means of testing large number of chemicals has significantly speeded up the process which allows us to find out if a particular compound has any therapeutic value for SMA.
- Early clinical trials are taking place
- Numerous research projects are underway (see The Work of the SMA Trust).
The Good News
Although there is no cure, advances in supportive therapies have led to increased longevity and improved quality of life, proving that the disease progress is amenable to change.
- Type I: Advanced nutritional and respiratory support has been shown to improve the longevity of children with Type I, with up to 50% of children living past 2 years old.
- Type II: Advances in respiratory support and management of scoliosis, a curved or rotated spine, have contributed to healthier lives with improved quality of life.
- Type III: Assistive devices and tailored programs have the capacity to increase independence and minimize disability.
Continued aggressive research efforts hold the key to a future treatment
The SMA Trust is dedicated to finding that cure
Download a SMA fact sheet PDF file for emailing or printing