This information sheet briefly explains the cause, effects, and management of Spinal Muscular Atrophy (SMA) Type 3. It includes sources of further information and support. It is written for the families of children diagnosed with SMA Type 3. It may also be useful for healthcare and other professionals.
SMA Type 3 is a complex condition; there is a lot of information to take in, and every child with SMA is different. Your child’s medical team will always be happy to go over any of this with you.
What is Spinal Muscular Atrophy?
Spinal Muscular Atrophy (SMA) is a rare, genetically inheritedneuromuscular condition. SMA may affect crawling and walking ability, arm, hand, head and neck movement, breathing and swallowing. SMA is often grouped into ‘Types’. Types of SMA are based on the age at which symptoms first appear and what physical ‘milestones’ a baby or child is likely to achieve. Milestones can include the ability to sit, stand, or walk.
There are four main types of SMA: Types 1, 2 and 3 appear in childhood; Type 4 appears in adulthood and is also known as Adult Onset SMA.
These ‘Types’ are not rigid categories. There is a wide spectrum of severity both between the different types of SMA and between children, young people, and adults within each type.
There are also other, even rarer, forms of SMA with different genetic causes including SMA with Respiratory Distress (SMARD), Spinaland Bulbar Muscular Atrophy (SBMA), and Distal SMA (DSMA).
What causes SMA?
Usually, electrical signals from our brain are sent down our spinalcord along our nerve cells and through to our muscles. This makes it possible for us to consciously contract our muscles and to make them move.
SMA affects a particular set of nerve cells called the lower motor neurones1 which run from the spinal cord out to our muscles. The lower motor neurones carry messages that make it possible for us to move the muscles we use to crawl and walk, to move our arms, hands, head, and neck, and to breathe and swallow.
For our lower motor neurones to be healthy, we need to produce an important protein called the Survival Motor Neuron (SMN) protein. Our ability to do this is controlled by a gene called Survival MotorNeuron 1 (SMN1)2.
We all have two copies of the SMN1 gene, one from each parent. People who have two faulty copies of the SMN1 gene have SMA. People who have one faulty copy of the SMN1 gene are carriers of SMA. Carriers do not have SMA or any symptoms of SMA. People who have two healthy copies of the SMN1 gene do not have SMA and are not carriers.
SMA is passed from parents to their children through their SMN1genes. When two people who are carriers have a child together, their child may inherit two faulty SMN1 genes, one from each parent. If this happens, then their child will have SMA.
Having two faulty SMN1 genes means that a child is only able to produce very low amounts of the SMN protein. This causes their lower motor neurones in their spinal cord to deteriorate. Messages from their spinal cord do not efficiently get through to their muscles, which makes movement difficult. Their muscles waste due to lack of use and this is known as muscular atrophy.
What is SMA Type 3?
SMA Type 3 is sometimes called Kugelberg-Welander disease. The symptoms of muscle weakness and floppiness (low tone / hypotonia) usually appear after 18 months of age but the actual age of onset is very variable and may not appear until late childhood or early adulthood.
Each child with SMA Type 3 is different but the onset of muscle weakness is gradual and children are generally able to walk until late childhood and sometimes into adolescence3.
Sometimes doctors try to indicate the degree of severity within SMA Type 3 by using a decimal classification4, for example, 3.1, 3.2, 3.5, 3.9. If you have any queries regarding this please speak to your child’s medical team.
Life expectancy for children diagnosed with SMA Type 3 is usually normal5 and most people live long, fulfilling, and productive lives.
How is SMA Type 3 diagnosed?
A doctor will diagnose SMA Type 3 after taking a medical history, physically examining your child, and by taking a blood sample for DNA testing. The blood sample is tested for a deletion mutation in the survival motor neurone 1 (SMN1) gene on chromosome 5. The result of this test is usually available within 2 – 4 weeks.
There may be uncertainty about the diagnosis, so further observations and muscle tests such as an electromyogram (EMG) or a muscle biopsy may be needed, which can take time.
Is there a treatment or cure for SMA Type 3?
Although there is currently no cure for SMA, this does not mean that nothing can be done. Symptoms can be managed so that your child can achieve their maximum mobility, independence, and quality of life.
What are the effects of SMA Type 3?
This section describes the effects of SMA Type 3 in general terms. But, it’s important to remember that each child with SMA Type 3 is affected differently and the severity of the condition varies from child to child.
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 from the centre of their body (distal muscles). Generally, children with SMA Type 3 find that their legs are weaker than their arms.
As your child grows, it may be difficult for their muscles to keep up with their daily activities. If your child has been able to, for example, walk or climb stairs, they may lose this ability as they get older. Some children may fall more easily as a result of their muscle weakness. If they are sitting on the floor they may need help getting up. About 50% of children with SMA Type 3 will lose the ability to walk independently by the age of 146 although some people are still able to walk in adulthood.
In SMA Type 3 the muscles supporting the spinal column are weakened. This means that some children will develop a sideways curvature of their spine6 (scoliosis). Also, because the condition reduces children’s ability to move, some joints may become tight (contractures) restricting their range of movement.
Muscle weakness in children with SMA Type 3 mainly affects their limb movement. It doesn’t affect bladder and bowel control but some children may need help with toileting, dressing, and undressing.
Children with SMA Type 3 may become weaker after infections and at times of major growth spurts such as puberty. SMA doesn’t affect a child’s sexual or intellectual5 development.
What healthcare and support is needed for SMA Type 3?
Your child should receive care from a multidisciplinary healthcare team, which can feel like a lot of people, but they all have an important role to play. You may have contact with specialists in some of the following areas: neuromuscular conditions; respiratorymedicine; orthopaedics; physiotherapy; occupational therapy; speech and language therapy; dietetics; and a hospital or community consultant paediatrician. If possible one of the team should be your keyworker whose job it is to help co-ordinate services for your family. (You can find out more about how these people help in our information sheet ‘Who’s Who of Professionals’.)
Children with SMA Type 3 should be seen by their medical team regularly to measure any change in their health and to offer advice and interventions at the right time. The aim is to enable your child to remain healthy and enjoy a good quality of life.
At every appointment with your child’s medical team you should be given time to ask questions and then jointly decide what support is best for your child.
Children with SMA Type 3 do not generally have difficulties with their breathing, but their breathing strength and cough effectiveness should be checked regularly.
You can read an overview of what good respiratory management involves in the booklet ‘Standards of Care for Spinal MuscularAtrophy – the family guide’7. As each child with SMA Type 3 is affected differently it’s important to discuss any queries you have with your child’s medical team.
A healthy diet is important for everyone. Your child’s health visitor and consultant will be able to provide advice and support on eating and nutrition.
Your child may become overweight if they have reduced mobility. If this happens the extra weight can increase the stress on muscles, bones and joints, making physical activity even more difficult. If needed, a dietician will be able to advise on a healthy diet that will suit your child.
Children with SMA Type 3 rarely have difficulty with their chewing and swallowing but your child’s medical team will provide you with advice and support if necessary.
Children with SMA Type 3 can become constipated which may cause discomfort. You can discuss how to manage this with your child’s medical team.
Children with SMA Type 3 have difficulties with their posture, movement, and mobility. Each child needs their own exercise routines designed by their physiotherapist to help with this. Routines may include exercises to help maintain their range of motion, reduce any discomfort, stretch any tight muscles, and prevent contractures. Regular, gentle stretching of their tight joints can help to reduce the pain that contractures can cause. If your child does have any pain, do talk to their doctor and physiotherapist. Your child might enjoy doing these exercises in the bath, or a swimming or hydrotherapy pool as the warm water aids buoyancy.
Regular, moderate exercise will also help your child to maintain their fitness and stamina and activities such as swimming and horse riding can be adapted to match their physical ability.
Although your child will lose muscle strength over time, it is important that they maintain activities like standing and walking for as long as possible. Walking can help delay the development of scoliosis3 and standing is good for breathing, blood circulation, bladder, bowels, bones and joints.
As your child’s physical abilities change, an occupational therapist will advise what sort of seating will give them the best, most comfortable support. This will make it easier for them to play with toys, eat independently, and join in at home and at school.
A physiotherapist will assess your child and provide appropriate equipment to support their standing, walking and positioning. Some children with SMA Type 3 benefit from having splints (sometimes called orthoses) for support with standing and walking. Types of orthoses include ankle foot orthoses (AFOs) and knee, ankle, footorthoses (KAFOs). These will be made specifically for your child by an orthotist who will explain how they will help.
Specialist equipment will enable your child to participate in activities both at home and at school. If your child finds walking increasingly difficult or they are having falls then they may benefit from using a walking frame or a manual wheelchair. If your child’s weakness increases, a powered (electric) wheelchair may help their independence. Your child’s physiotherapist and occupational therapist will be able to advise you about walking aids and wheelchairs.
As already mentioned, children with SMA Type 3 may develop a sideways curvature of their spine (scoliosis). It is important that the medical team monitors your child regularly so that any increase in curvature is noticed early. This is more likely to develop if your child is no longer able to walk3. The degree of the curvature and your child’s age will be factors in deciding how to manage this. Initially this may be with a spinal brace or jacket but surgery to correct scoliosis may be recommended if the scoliosis is contributing to breathing difficulties, is preventing comfortable sitting, or if the curvature has progressed beyond a certain point.
Occupational therapists can give you advice about other adaptations and equipment that will help with your child’s everyday activities such as writing, playing, washing, dressing, cooking and eating, both at home and at school. With appropriate encouragement, adaptations, and support, your child will be able to lead as fulfilling a life as their friends.
What other help is available?
A diagnosis of SMA Type 3 with all its complexity can have an enormous impact on families. It’s important for you and your child to have emotional support and plenty of time to talk and ask questions. This can be with members of your child’s medical team, your local G.P., health visitor, social worker, psychologist or a counsellor.
To enable your child to participate fully in activities at home, school, and in their community, you will need information, advice and support on mobility, education, equipment and sources of funding that will aid their inclusion. You can find out more by talking to your child’s healthcare team, Spinal Muscular Atrophy Support UK (SMA Support UK), and the other people and agencies listed in this leaflet.
SMA Support UK can provide information and support to families affected by SMA in the UK. Our Outreach Workers are able to visit you at home and can discuss with you the health, social, educational, financial, and care support that you and your child may be entitled to. We can also put you in touch with our Peer Support Volunteers who have personal experience of living with SMA Type 3. Information about these services is available on our website or please phone us on 01789 267 520 or email: [email protected]
The Muscular Dystrophy Campaign (MDC) also provides information, support and advocacy services, including grants towards specialist equipment, for people affected by a range of neuromuscularconditions. Visit their website or you can phone them on 0207 803 4800 or email: [email protected]
Regional care advisors, and sometimes neuromuscular nurse specialists, are attached to NHS neuromuscular clinics in various regions of the UK. They provide support and information to children and adults with muscle diseases and their families. They link up with other professionals and services so that people receive the local health and social support they need. Regional care advisors’ contact details are available on the MDC’s website.
Families living in the UK may be eligible for a number of financial benefits to help towards the cost of providing the extra care their child may need. This does depend on your individual circumstances.
For further information about financial benefits visit the Gov.UK website and look at the sections ‘Benefits’ and ‘Carers and Disability Benefits’. The Department of Work and Pensions (DWP) can be contacted on: 0345 608 8545.
Contact a Family provide information and support to families who have a child with a disability. This includes information on benefits and grants. They can be contacted on 0808 808 3555 or through theirwebsite.
Your health visitor, neuromuscular care advisor, family support worker, social worker or outreach worker may be able to help you with applications for financial benefits.
There are also a number of charities that may assist you with the cost of general household goods, specialist equipment, and holidays / days out. Please contact SMA Support UK for more information.
As a parent with a child with SMA you should be offered a referral forgenetic counselling to help you understand how SMA is passed on and what the chances are of other people in your family being affected. Genetic counselling also provides you with the opportunity to discuss your choices for any future pregnancies.
As your child and any siblings grow up, they can also ask for genetic counselling, particularly if they are considering having children.
For more information on the genetics of SMA, the chances of having a child with SMA and the tests that can be carried out, please see ourGenetics of Spinal Muscular Atrophy leaflet.
What does the future hold?
To find out more about SMA research go to the research pages.
As new treatments for SMA are being developed they need to be tested in clinical trials but because SMA is a rare condition it can sometimes take years to find enough patients for a clinical trial. The UK SMA Patient Registry is a database of genetic and clinicalinformation about people affected by SMA which aims to speed up this process. The Registry also helps specialists gain more knowledge about the condition and the number of people affected by SMA. This information helps to develop and improve worldwide standards of care for people with SMA. You can find out more by looking at their website, emailing: [email protected] or phoning: 0191 241 8617.