The purpose of this information sheet is to provide a brief overview of the causes and effects of Spinal Muscular Atrophy with Respiratory Distress and how it is inherited. It includes sources of further information and support. The sheet is written for families of children diagnosed with SMARD, professionals (health, care and others) and members of the general public.
A glossary is available at the end of the information sheet to explain medical terms which appear in bold font. If you find any of the information difficult to understand, please discuss this with the medical team working with your child.
What is SMARD?
SMARD stands for Spinal Muscular Atrophy with Respiratory Distress. It is a severe, inherited neuromuscular condition that specifically affects nerve cells in the spinal cord called lower motor neurones. In SMARD, the lower motor neurones degenerate, impairing the link between the brain and muscles. These muscles can no longer be stimulated, which causes them to atrophy, or wither, due to inactivity.
The muscles used in breathing are severely affected in SMARD. The diaphragm is a large, thin sheet of muscle that seperates our chest from our stomach. It is essential for normal breathing. In SMARD the diaphragm is paralysed. This leads to respiratory distress, which is often the first and most noticeable clinical symptom. It usually occurs in the first year of life. Some signs may be present before birth - some babies do not put on weight at the expected rate for their age and gender and some mothers may notice a reduction in their baby's movements towards the end of the pregnancy1.
Muscle weakness progresses rapidly after the onset of respiratory distress. The muscles affected are those which enable walking, crawling, arm and hand movement, head and neck movement, and swallowing. Distal muscles, those furthest from the centre of the body, are the most severley affected. That is, muscles in the hands and feet. Foot deformities and a weak cry can sometimes be early symptoms of SMARD. Children with SMARD are usually unable to walk.
The autonomic nervous system may also be affected. This may result in symptoms such as excessive sweating, cardiac arrhythmia (an irregular rate or rhythm of the heart), constipation and bladder incontinence2.
SMARD is an extremely rare disease and the number of children affected is very small. Currently it is not possible to collect accurate numbers of those affected. This will probably change as knowledge of the condition increases.
What causes SMARD?
SMARD is an autosomal recessive genetic disorder, meaning that two faulty copies of the disease gene have to come together, one from each parent, for the disease to occur. When both parents carry a faulty copy of the disease gene, there is a 1 in 4 chance in each pregnancy of the baby being affected by SMARD.
SMARD is a genetically varied condition. SMARD1 is caused by mutations in the IGHMBP2 gene(immunoglobulin mu-binding protein 2) on chromosome 11q13-q212. It is sometimes called autosomal recessive Distal Spinal Muscular Atrophy 1 (DSMA1) or Distal Hereditary Motor Neuronopathy Type VI3.
In addition to SMARD1 / DSMA1 there are other forms of SMARD that have a later onset, such as DSMA2, DSMA3, DSMA4 and DSMA5. These are caused by mutation on different genes and chromosomes.
The variety of genetic causes and use of different names can be very confusing for families. As research continues, more information about the genetic variants may become available.
How is SMARD diagnosed?
SMARD is a very rare condition, which may sometimes go unrecognised. Obtaining a diagnosis can be a lengthy process - it may take several months and in some cases it may not always be possible to confirm the diagnosis.
If SMARD is suspected, a blood sample will be taken for genetic testing to help confirm the diagnosis. Further tests, such as electromyogram (EMG) or muscle biopsy, may be considered if there is uncertainty about the diagnosis.
SMARD is usually diagnosed within the first year of life when the child develops severe respiratory distress and presents as a medical emergency. Once a child with SMARD starts to show symptoms of respiratory failure they will requiremechanical ventilationto survive. This means that, following diagnosis, discussions need to take place between the child's parents and the medical team regarding the different management options and which would be most appropriate for their child's circumstances.
How does SMARD progress?
There is a wide range of severity in SMARD. Some children are very weak and show symptoms within the first 2 - 3 months of life. Other children are relatively strong and are usually diagnosed later on in the first year of life. Also, how SMARD progresses can vary widely between individual and children1.
Typically the health of a child with SMARD will deteriorate rapidly within the first two years of life. This may be followed by a period when the child's health remains stable (this may be described as a disease plateau) or may even show some improvement after the age of two years4.
Is there a treatment or cure for SMARD?
There is currently no cure or treatment for SMARD. When a child is diagnosed, their parents and medical team will need to openly discuss which possible medical interventions are in the best interest of the child.
This should assist in developing a plan for the child's care, including care in a medical crisis. Broadly speaking this may focus on palliative care services or more invasive medical management involvingtracheostomyfollowed by long term ventilation.
These are very difficult decisions and parents should have time and support to discuss them thoroughly. This discussion will be with the medical team who have the knowledge of the child's condition and possible progression. Parents may also want to seek emotional support from other sources outside the medical team, e.g. their family, community, spiritual leaders.
What other help is available?
In addition to the care and support provided by a child's medical team, The Jennifer Trust Support Services Team can provide information and support to families in the UK affected by SMARD. Our Outreach Workers are able to visit families whose baby has been diagnosed with SMARD. They offer personalised support and information and are available to answer questions. They can help families understand SMARD and can discuss the support they may be entitled to. We can put families in touch with one of our Peer Support Volunteers who has personal experience of living with SMARD. Multisensory toy packs are available for babies diagnosed with SMARD in the UK. We can also put families in touch with other support organisations in the UK which offer practical and financial support.
For more information about our services, please contact us on 01789 267520 or email
Whilst every effort is made to ensure that the information on these web pages is complete, correct and up to date, this cannot be guaranteed and the Jennifer Trust shall not be liable whatsoever for any damages incurred as a result of their use. The Jennifer Trust does not necessarily endorse the services provided by the organisations listed on these web pages.