SMARD1 is an inherited nervous system condition that causes muscle weakness and respiratory failure. Symptoms usually start to show between the ages of 6 weeks and 6 months. It is an extremely rare disease. The number of children affected is very small.

The first and most noticeable symptom of SMARD1 is usually breathing difficulties (respiratory distress). These are caused by the large, thin sheet of muscle separating the chest from the stomach (the diaphragm) that is essential for normal breathing becoming paralysed.

After breathing difficulties start, signs of weakness in the muscles that are furthest from the centre of the body (distal muscles) usually progresses rapidly. This weakness shows first in the hands and feet. It then spreads to all muscles, but within 2 years the muscle weakness usually stabilises. This is sometimes described as a ‘disease plateau’.

A child’s walking, crawling, arm and hand movement, head and neck movement and swallowing may all be affected. Exactly how each child is affected varies. Some children may still have some ability to move their muscles while others lose this ability completely.

Other early symptoms of SMARD1 can include a weak cry and misshapen feet. For some children, fatty finger pads are another symptom.

SMARD1 may also affect nerves for sensation (called sensory neurons) and control of body functions (the autonomic nervous system). This can lead to symptoms such as excessive sweating, an irregular heart rate or rhythm (cardiac arrhythmia), constipation, bladder incontinence and a reduced response to pain.

Sadly, life expectancy for babies who have SMARD1 is severely reduced. It is difficult though to predict life expectancy for any individual child. The progression of SMARD1 and appropriate medical interventions to support breathing varies between children.

Usually, nerve cells called lower motor neurons carry electrical signals from the brain to the muscles and make it possible to move them. In SMARD1, due to the changes in genetic material, the lower motor neurons degenerate. This affects the link between the brain, the spinal cord and muscles. The muscles can no longer be stimulated, which causes them to waste or atrophy.

More than 60 different mutations in the IGHMBP2 gene have been found to cause SMARD1. Most of these affect either the amount or efficiency (functionality) of the IGHMBP2 protein produced by the IGHMBP2 gene.

Although the exact mechanism is unknown, if the IGHMBP2 protein is not working properly, or there isn’t enough of it, the lower motor neurons degenerate.

It is thought that the amount of working or ‘functional’ protein the altered IGHMBP2 gene produces may be linked to the severity of a child’s SMARD1. The less functional IGHMBP2 protein a child has, the earlier they are likely to develop symptoms. However, many differences have been seen even between individuals who have identical changes in the IGHMBP2 gene. This suggests that other factors may also have an effect.

As SMARD1 is a very rare condition, it sometimes does not get recognised. It can take a very long time to get an accurate diagnosis – perhaps several months. Sometimes it is not possible to confirm the diagnosis.

A child is usually diagnosed if they have been in hospital with severe breathing difficulties. If doctors think this could be caused by SMARD1, a blood sample is taken for genetic testing to help confirm the diagnosis. If they are still unsure, they may ask for further tests, such as an electromyogram (EMG) or muscle biopsy.

As one parent said:

"Looking for the genetic confirmation for SMARD1 can be a bit like looking for a spelling mistake in a novel".

When your child’s diagnosis is confirmed, they may already be under the care of specialists in neuromuscular conditions and respiratory care. If not, you would expect to have a referral to these specialists so that you can meet to discuss next steps. Though families are prepared to travel, infants with SMARD1 may not cope well with a long journey. Where this discussion takes place will very much depend on how well your child is and where the nearest specialist centre is.

Although there is currently no treatment or cure for SMARD1, there are options to manage your child’s care. The aim is to give them the best possible quality of life and for them to be as comfortable as possible. As there is such a wide range of severity and impact with SMARD1 and family circumstances vary greatly, discussions are very individualised.

At first these are likely to be of greatest concern. Once a child with SMARD1 starts to show symptoms of severe breathing difficulties, they will need a lot of help to survive. This can involve the need for surgery to create an opening in their windpipe so that they can breathe through a tube rather than their mouth (a tracheostomy). This is a very big step. Any family facing this option will have a full and careful discussion with their specialists as to whether this is best for their child.

Though it is a difficult discussion, it is important that you have the earliest possible opportunity to discuss the range of future care options with your medical team.  They can then record the treatment you do or do not wish your child to have if their health deteriorates or in an emergency.

Managing your child’s complex and potentially life-threatening condition will  affect you and all your family. You will need a lot of support from a number of different health professionals and the palliative care services.

All these professionals will work as a team aiming to actively support your child and family’s physical, emotional and practical needs.

If it is possible for you to take your child home, some of the professionals may be based in your local hospital or children’s hospice. As well as your child’s neuromuscular and respiratory specialists, your team may include specialists in:

• physiotherapy
• orthopaedics
• occupational therapy
• speech and language therapy
• dietetics
• community nursing

If you are able to go home, you will need a great deal of practical support. A detailed ‘care package’ will be set up before your child is discharged from hospital. This often takes a long time to organise and is likely cover the following topics:

• Housing
• Equipment and supplies
• Day and night-time carers / who will provide this service / hours and rotas
• Short breaks / respite care
• Procedures to cover emergencies
• Getting out and about – including play, leisure and education
• Sources of financial help
• Sources of support – including those in your local area

You should also receive information and advice about other financial, practical and emotional support available in your local area.

With your permission, your child’s emergency advance care plan can be shared with all the professionals supporting your child, including ambulance services, so that everyone is aware of your wishes. You should have your own copy so that you can give it to hospital services if you are away from your home area.

Your local children’s hospice is there to support families, both practically and emotionally. They provide support and breaks from caring from diagnosis onwards. As well as offering nursing care, they provide a range of services that may include physiotherapy, complementary therapies, play and music therapy.

They can support you with your baby’s ongoing and future care should they become very unwell. They can also offer invaluable practical and emotional support and specialist care if, sadly, you are faced with the end of your child’s life. This may be within the hospice and in some areas in your own home.

The impact of a diagnosis of SMARD1 on families is enormous. It often comes as a huge shock. You may experience feelings of disbelief, confusion, anger and sadness. You may find it difficult to take everything or anything in. The 24 hour-a-day responsibility of caring for a child with complex medical needs that follows can be physically, emotionally and psychologically exhausting.

Everyone is different, but it is important that you and your family have access to emotional support and plenty of time to talk and ask questions. This can be with members of your child’s medical team, your local General Practitioner (GP), health visitor, social worker, psychologist or a counsellor, as well as family and friends, a spiritual leader, support groups, or online communities.

Even though you will be focused on your child, try and look after yourself too. Things like remembering to keep up to date with your own health checks and getting the ‘flu’ jab are important. Perhaps ask friends and family to help out with practical jobs such as shopping and cleaning which can help save you some time and energy.

You may also find it helpful to use local short break services. These may be possible at your home or at a children’s hospice. Ask your GP, community nurse, health visitor or social worker for more information.

Families living in the UK may be eligible for a number of financial benefits to help towards the cost of providing the extra care your child needs. This does depend on your individual circumstances. For further information, see  Living With SMA – Financial Support & Benefits >

Your health visitor, community nurse, neuromuscular care advisor, family support worker, social worker or outreach worker may be able to help 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 UK’s Community Support Team for more information.

A genetic counsellor is a healthcare professional who has expert training in genetics. They will explain how SMARD1 is inherited and what the chances are of other family members also being affected. Genetic counselling also provides the opportunity to discuss options and choices for any future pregnancies.

Following your child’s diagnosis, you should be offered genetic counselling. A referral to genetic services is usually made through your General Practitioner (GP), paediatrician or neurologist.

Though there is very limited into SMARD 1, what we do find out we report in our SMARD Research page >.

Patient Registries are databases of genetic and clinical information about people with a particular condition. They provide points of contact for when new treatments develop that need to be tested in clinical trials. They also help specialists gain more knowledge about the condition and the number of people affected. This helps to develop and improve worldwide standards of care for people with the condition.

Currently in the UK there is no specific Patient Registry for SMARD1. The UK SMA Patient Registry is mainly for people affected by SMA due to mutation in the SMN1 gene (known as 5q SMA). However, the registry does accept registrations from those affected by SMARD1 who have the altered IGHMBP2 gene.

SMA UK

• Phone: 01789 267 520
• Email: office@smauk.org.uk
• Website: www.smauk.org.uk

Our Community Support Team > offers a free confidential UK-wide service. We don’t provide medical services or advice. But, we can give emotional support, practical advice, and guidance. We do this by email, phone, text, or virtual or face-to-face meetings.

You can ask for a free Multisensory toy pack if you live in the UK and your child is under 12 months of age and has been diagnosed with SMARD1.

The Living With SMA / Children area of our website builds on knowledge and advice from the SMA Community and SMA UK’s Support Services team. It covers a whole host of topics that might be useful including equipment, homes,  transport, emotional and social support. The Health & Wellbeing section focuses on care for those who have 5qSMA so is not relevant for families affacted by SMARD1.

Children’s hospices

Located throughout the UK, these also offer a wide range of services and support to eligible children and families; some also offer short breaks. Details of hospice services are available from Together for Short Lives / Children’s Hospices > 

Together for Short Lives

• Phone: 0808 8088 100
• Website: www.togetherforshortlives.org.uk

Provide information and support to families who have a child with a life-limiting condition.

Contact

• Phone: 0808 808 3555
• Website: www.contact.org.uk

Provide information and support to families who have a child with a disability.

1. Pitt et al. (2003) Severe infantile neuropathy with diaphragmatic weakness and its relationship to SMARD1. Brain 126: 2682-2692.

2. https://www.omim.org/entry/604320 (last accessed 18th September 2024)

General References

Eckart. M, Guenther. U, Idkowiak. J, Varon. R, Grolle. B, Boffi. P, Van Maldergem. L, Hubner. C, Schuelke.M, von Au. K (2012) The natural course of infantile spinal Muscular atrophy with respiratory distress type 1 (SMARD 1) Pediatrics 2012; 129;e148

van der Pol. WL et al 190th ENMC international workshop: Spinal muscular atrophy with respiratory distress/distal spinal muscular atrophy type 1 (2103) http://dx.doi.org/10.1016/j.nmd.2013.04.004 (accessed 18th September 2024)