An overview of SMA – Spinal Muscular Atrophy
Source: http://www.smasupportuk.org.uk
- In the UK, approximately 100 children are born with this rare disease each year.
- One in every 6,000 – 10,000 babies are born with the condition.
- At any one time it is thought that there are between 2,000 – 2,500 children and adults in the UK living with SMA.
- How do people get SMA?
- SMA is an autosomal recessive genetically inherited neuromuscular disease. This means that two faulty copies of the disease gene, one from each parent, are needed for a person to have the condition.
- When two SMA carriers have a child together, there is a 1 in 4 (25 %) chance that the child will have inherited both faulty copies of the SMN1 gene and will develop SMA. These chances are the same for each pregnancy.
- When two SMA carriers have a child together, there is a 1 in 2 (50 %) chance that the child will be a carrier. Approximately one in 40 – 60 people is an SMA carrier, which equates to about 1.5 million people in the UK.
- What is SMA1?
- SMA Type 1 is the most severe form of SMA. It accounts for between 50 – 70% of cases of childhood onset SMA. It is sometimes called Werdnig-Hoffman Disease or severe infantile SMA.
- Each baby with SMA Type 1 is different. The symptoms of SMA Type 1 usually appear within the first few months of life.
- At present there is no cure for SMA, and no treatment that will repair the damage to the lower motor neurons or reverse the weakening of the muscles. However there is a range of options aimed at managing symptoms, reducing complications of weakness and maintaining the best quality of life for as long as possible.
- What are the effects of SMA Type 1?
- The following describes the effects of SMA Type 1 in general terms. But, it’s important to remember that each child with SMA Type 1 is affected differently and the severity of the condition varies from child to child.
- Babies with SMA Type 1 are often described as ‘floppy’ babies, due to their low muscle tone (hypotonia) and severe muscle weakness. The muscle weakness affects movement, swallowing and breathing. Babies with SMA Type 1 are unable to lift their heads, have difficulty rolling over and are unable to sit unsupported. They may also have a weak cry.
- Children’s muscle weakness is usually the same on both sides of their body (symmetrical). The muscles closest to the centre of their body (proximal muscles) are usually more severely affected than the muscles furthest away from the centre of their body (distal muscles). Generally, babies with SMA Type 1 have weaker legs than arms. Babies have difficulty lifting their arms and legs, while still being able to use their hands and fingers.
- Weakness of the respiratory muscles can cause severe difficulties with breathing and coughing. It can also increase the chance of respiratory infections, which can be life-threatening.
- The muscles used for sucking and swallowing are also affected and this may cause difficulty with feeding and weight gain. Difficulty with swallowing can increase the risk of fluids or food passing into the lungs (aspiration), which can cause choking and, in some cases, pneumonia.
- The brain is unaffected and babies affected by SMA Type 1 are often described as bright, alert and responsive. The muscles of the face are not usually affected so babies can smile and frown.
- Though it is not possible to accurately predict, for the majority of children (approximately 95%) life expectancy is less than 18 months.