Symptoms, Diagnosis & Effects of 5q Spinal Muscular Atrophy

Many people – families, friends and professionals who haven’t come across SMA before – will want to know more about its symptoms, how it’s diagnosed and what impact it may have.

This guide explores these questions for the most common form of SMA, known as 5q SMA due to its genetic cause. When a child or adult is first diagnosed with 5q SMA, the doctor gives a clinical classification - SMA Type 1, 2, 3 or 4 - which reflects the age of symptom onset and the motor milestones that someone would be expected to achieve. Drug treatments are starting to change these expectations.

This page tells you more about:

How is 5q SMA diagnosed?

Clinical classification of 5q SMA

Importance of other information

Symptoms and effects of SMA Types 1, 2, 3 and 4

As you read this guide, please remember that:

  • Although 5q SMA is clinically classified into different ‘Types’ which reflect the severity of its impact, it is considered a spectrum.
     
  • For children and adults, the severity of the condition varies from person to person, both within and between ‘Types’ - each child and adult is affected differently.
     
  • Care and management as recommended in the International Standards of Care for SMA1-3 is essential.
     
  • The physical milestones describing people’s ability to sit, stand and walk are increasingly important when it comes to making decisions about care and how to manage symptoms.
     
  • For simplicity, the summary words ‘non-sitters’, ‘sitters’ and ‘walkers’ are often used.
     
  • Treatments that may change the impact of a person’s SMA are starting to become available.
     

How is 5q SMA diagnosed?

Parents / carers will often have been concerned about symptoms of weakness in their child. Symptoms may have been noticed by doctors or the health visitor or community nurse.

Adults who are diagnosed with SMA Type 4 may have had concerns about their muscle weakness or fatigue.

Any child or adult with suspected SMA will be physically examined. This may be by their GP, paediatrician, neurologist or neurological specialist, who will ask about their medical history and concerns. A GP may have met few, or even no, children or adults who have SMA, so should make an immediate referral to a specialist Neuromuscular Centre. If SMA is suspected, a blood sample for DNA testing will be arranged. The sample is tested for a deletion mutation in the Survival Motor Neuron 1 (SMN1) gene on chromosome 5. It’s also now recommended1,2 that the number of SMN2 copies is assessed as this can be a helpful indicator of what effects the condition will have. Entry criteria for clinical trials and new drug treatments often specify the number of SMN2 copies someone must have to be eligible. For more information on SMN2 copies, see our information sheet, ‘What is 5q Spinal Muscular Atrophy?’.

The SMN1 deletion test result is usually available within 2 – 4 weeks. Other tests may take longer. If there’s any uncertainty about the diagnosis, further tests, such as an electromyogram (EMG) to record the electrical activity of muscles, may be discussed, but this isn’t usually needed to confirm 5q SMA.
 

Clinical classification of 5q SMA - ‘Types’

There is a wide spectrum of how severely children, young people and adults are affected, both within and between ‘Types’. Broadly, though, they are as follows:

SMA Type

Usual age of symptoms Impact of muscle weakness on sitting / walking
Type 1 Younger than 6 months Unable to sit or roll independently
Type 2 6 - 18 months Able to sit, but not walk, independently
Type 3a 18 months - 3 years Able to walk, though may lose this ability over time
Type 3b 3 years - 18 years Able to walk, though may lose this ability over time. 
Type 4 Over 18 years Mild walking difficulties

*Adapted from Finkel et al., 20174


The importance of other information

Improvements in care and management and, more recently, the development of new drug treatments has increasingly meant that it is essential that other information about a person’s SMA is needed to help with management and treatment decisions. These in turn may change the future impact of the condition on the person.

Length of time since symptom onset can be very important when it comes to treatment decisions. In general, evidence suggests that early treatment may be necessary to maximise the potential benefits.

Though a significant achievement, drug treatments are not a cure and must go hand in hand with the best supportive care and management of symptoms, which is outlined in the ‘International Standards of Care for SMA’ (SoC)1-3. Information such as how someone’s breathing ability is affected by their SMA and whether they are able to sit, stand or walk are very important when it comes to which care and management guideline applies to which groups of children and adults. For simplicity the following summary words are used in the SoC:

non-sitters - those who are unable to sit

sitters - those who are able to sit but not walk

walkers - those who are able to walk


SMA Type 1

Symptoms and effects usually begin from birth or within the first few weeks or months of life. Generally, the earlier the onset of symptoms, the more severe the condition. Each child is affected differently but, in general, babies with early onset SMA are:

  • bright, alert and responsive; their intelligence isn’t affected
  • able to smile and frown as their facial muscles aren’t severely affected
  • often described as ‘floppy’ babies due to their low muscle tone (hypotonia) and severe muscle weakness
  • unable to support or lift their head due to their weak neck muscles
  • unable to sit unsupported and have difficulty rolling over
  • able to move their hands and fingers but have difficulty lifting their arms and legs

They have:

  • weak breathing muscle weakness, which can cause a weak cry and difficulties with breathing and coughing
  • an increased chance of chest infections, which can be life-threatening
  • difficulty swallowing their saliva and other secretions, which may make them sound chesty or make them cough
  • difficulties feeding and gaining weight
  • an increased risk of fluids or food passing into their lungs (aspiration), which can cause choking and, sometimes, chest infections or pneumonia

Please see our guide for parents and carers: 'Looking after your child with SMA who has had a recent diagnosis of SMA Type 1'.

The family-friendly guide to the Standards of Care (SoC) for SMA was agreed by a committee of international healthcare and patient experts. Find it here.

Living With SMA has a wide range of information and ideas for daily living.

 

Sometimes SMA can affect babies even before birth; this may be called SMA Type 0.

Before 2007, without intervention for breathing difficulties, most children were expected to live for less than two years5. The November 2017 ‘International Standards of Care for SMA’ refer to evidence that suggests that since more proactive managements were introduced in 2007, children have been living longer1,2.

Since late 2016, the gradual worldwide introduction of drug treatments has been further changing outcomes positively for children who have SMA Type 1, especially for newly diagnosed infants. In general, both clinical trial and real-world evidence suggests that early treatment is necessary to maximise the potential benefits.

Global clinical trials and follow-up studies of possible drug treatments for those who have SMA Type 1 had tended to focus on their impact on motor milestones and survival. There is more understanding now of the importance of respiratory outcomes, and the value of other outcomes, that impact on a child’s quality of life, such as the development of:  swallowing, feeding / eating; verbal communication; muscle support of spine and hips; fine motor skills and fatigue levels.

In the UK, drug treatment (NHS funded) is now possible for many children who have SMA Type 1.

For more information about emerging treatments and associated clinical trials, see this page.


SMA Type 2

Symptoms and effects usually begin between 6 and 18 months of age. Generally, the earlier the onset of symptoms, the more severe the condition.

Each child is affected differently, but in general, children with SMA Type 2 are usually bright and engaging. However, due to SMA, they are likely to experience:

  • muscle weakness on both sides of their body
  • muscle weakness closest to the centre of their body; these are more severely affected than muscles furthest away
  • difficulties moving their arms, but hands and fingers less so
  • difficulties lifting their legs
  • legs that are weaker than arms

As they get older, their intellectual and sexual development5 isn’t affected, but SMA usually causes them to have:

  • muscle weakness that may make it difficult for them to keep up with their daily activities. For example, if they have been able to crawl or roll, they may lose this ability.
  • weak breathing muscles, making it difficult for them to cough effectively and more vulnerable to chest infections.
  • muscles supporting the spinal column that are weak; most children develop sideways curvature of their spine6 (scoliosis).
  • reduced ability to move so that some joints may become tight (contractures), further restricting their range of movement.

SMA Type 2 can weaken chewing and swallowing muscles. For some children, their tongue and shoulder muscles may twitch and they may have a slight tremor in their hands7.

Major growth spurts, such as puberty, often create greater demands on weak muscles. SMA Type 2 can also mean that children and adults have a tendency to become weaker after infections.

Children and adults will need help with daily tasks like washing, dressing and undressing. Though their bladder and bowel control isn’t usually affected, they will need help transferring from their wheelchair to the toilet.

Serious complications (such as severe respiratory infections) are associated with reduced life expectancy8, but improvements in healthcare standards mean that the majority of people live long, fulfilling lives.

Please see our guide for parents and carers: Looking after your child with SMA who has had a recent diagnosis of SMA Type 2.

The adult and family-friendly guide to the Standards of Care (SoC) for SMA was agreed by a committee of international healthcare and patient experts. Find it here.

Our Living With SMA website area for parents, teenageers and adults,has a wide range of information and ideas for daily living.

Serious complications (such as severe respiratory infections) are associated with reduced life expectancy8, but improvements in healthcare standards mean that the majority of people live long, fulfilling lives.

Since late 2016, the gradual worldwide introduction of drug treatment for children and adults who have SMA Type 2 has seen positive outcomes. In general, both clinical trial and real-world evidence suggests that early treatment is necessary to maximise the potential benefits.

Global clinical trials and follow-up studies of possible drug treatments for those who have SMA Type 2 had tended to focus on their impact on motor milestones gained in childhood.  There is more understanding now of the importance of respiratory outcomes, and the value of other outcomes, that impact on quality of life for older children, young people and adults, such as fine motor skills and fatigue levels which enable or maintain independence in daily living. In 2019, 96.7% of 1,327 validated responses to SMA Europe’s survey of people diagnosed with SMA stated they would “consider it to be progress if there was a drug to stabilize their current clinical state.”9

In the UK, drug treatment (NHS funded) is now possible for some children and adults who have SMA Type 2.

For more information about emerging treatments and associated clinical trials, see this page.


SMA Type 3

The symptoms and effects of SMA Type 3a usually begin between 18 months and 3 years.

The symptoms and effects of SMA Type 3b usually begin after 3 years, but before adulthood.

Each child is affected differently, but in general, children with SMA Type 3 are bright and engaging. However, their SMA causes:

  • muscle weakness on both sides of their body
  • muscle weakness closest to the centre of their body as these muscles are more severely affected than muscles furthest away
  • legs that are weaker than arms

As they get older, their intellectual and sexual development5 isn’t affected, but their SMA usually causes them to have:

  • difficulties with standing and walking. This usually happens later for children with SMA Type 3b than for children who develop symptoms at an earlier age.
  • difficulties keeping up with daily activities. For example, if they have been able to walk or climb stairs, they may lose this ability. Some children may fall more easily because of their muscle weakness. If they’re sitting on the floor, they may need help to get up.
  • muscles supporting the spinal column that are weakened. This means that some children develop a sideways curvature of their spine6 (scoliosis).
  • a reduced ability to move due to some joints becoming tight (contractures), restricting their range of movement.
  • a tendency to become weaker after infections and at times of major growth, such as puberty.

Some children, young people and adults will need help with daily tasks like washing, dressing and undressing. Though their bladder and bowel control isn’t affected, some may need help getting to, and sitting on, the toilet.

Fewer people with SMA Type 3 have swallowing or breathing difficulties and their life expectancy isn’t affected10. Most people live long, fulfilling lives.

Please see our guide for parents and carers: Looking after your child with SMA who has had a recent diagnosis of SMA Type 3’.

The adult and family-friendly guide to the Standards of Care (SoC) for SMA was agreed by a committee of international healthcare and patient experts. Find it here.

Our Living With SMA website area for parents, teenagers and adults has a wide range of information and ideas for daily living.

Since late 2016, the gradual worldwide introduction of drug treatment for children and adults who have SMA Type 3 has seen positive outcomes. In general, both clinical trial and real-world evidence suggests that early treatment may be necessary to maximise the potential benefits.

Global clinical trials and follow-up studies of possible drug treatments for those who have SMA Type 3 had tended to focus on their impact on motor milestones gained in childhood.  There is more understanding now of the value and importance of respiratory and other outcomes that impact on quality of life for older children, young people and adults, such as fine motor skills and fatigue levels which enable or maintain independence in daily living. In 2019, 96.7% of 1,327 validated responses to SMA Europe’s survey of people diagnosed with SMA stated they would “consider it to be progress if there was a drug to stabilize their current clinical state.”9

In the UK, NHS funded treatment is now possible for some children and adults who have SMA Type 3.

For more information about emerging treatments and associated clinical trials, see this page.


SMA Type 4

Symptoms and effects begin in adulthood.

Each person is affected differently but, in general, symptoms can include:

  • tired, aching muscles
  • a feeling of heaviness
  • numbness
  • cramp
  • a slight shaking of the fingers and hands
  • fatigue

SMA Type 4 usually progresses slowly over time, causing increased muscle weakness with age. This may impact on daily living activities, such as walking, dressing and bathing.

SMA Type 4:

  • rarely affects swallowing or breathing
  • doesn’t affect intelligence, and life expectancy isn’t affected11.

SMA Type 4 affects the lower motor neurons. This is different from Motor Neurone Disease (MND), also known as Amyotrophic Lateral Sclerosis (ALS) which affects both the upper and lower motor neurons. Though SMA is also classed as a motor neuron disease, it isn’t MND. Whereas MND is almost always life-limiting, SMA Type 4 isn’t.

Access to treatments for those clinically diagnosed with SMA Type 4 varies between countries. This may depend on the decision made by the regulatory authorities – for example in some countries it is approved for all who have 5q SMA. It may also depend on how distinct the ‘onset of symptoms’ age boundary is considered to be between Type 3b and Type 4.

In the UK now, access to drug treatment (NHS funded) is only possible for those who have a clinical diagnosis of SMA Type 1, 2 or 3 (see table page 1) and who meet other eligibility criteria. No drug treatments are currently available in the UK for people who have been given the clinical classification / diagnosis SMA Type 4, which should include careful review of the history of the person’s onset of symptoms.

Please see our guide: Looking after yourself if you're an Adult who has had a Recent Diagnosis of SMA’.

The adult and family-friendly guide to the Standards of Care (SoC) for SMA was agreed by a committee of international healthcare and patient experts. Find it here.

Living With SMA has a wide range of information and ideas for daily living.


Resources and Support

The International Standards of Care for Spinal Muscular Atrophy (2017) can be read / downloaded from here.

For more information about the causes and genetics of 5q SMA, please see our information sheets:

  • ‘What is 5q Spinal Muscular Atrophy?’
  • ‘The Genetics of 5q SMA’

You can find these here.


SMA UK

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

We provide a free Support & Outreach Service for families and adults by email, phone, text or a virtual meeting. When covid-safe we can offer an outreach home visit. Our experienced team offers personalised support and information and is available to answer questions and talk things through. Though we don’t give medical advice, we can discuss support options with you.

We also support health, education and social care professionals.

If you're wondering about an aspect of life with SMA, we hope the Living With SMA area of our website will be a helpful starting point, giving you useful information and ideas. It builds on knowledge and advice from the SMA Community and SMA UK's Support Services Team. It covers a whole host of topics, including: health & wellbeing, equipment, homes, education, work, transport, leisure, holidays, financial, and emotional & social support: www.livingwithsma.org.uk

SMA UK’s monthly E-news keeps the community up-to-date and includes the latest research and treatment updates. You can sign up here.

Version 2
Author: SMA UK Information Production Team
Last full review: September 2020
Last updated: May 2021
Interim review due: November 2021
Next full review due: September 2023

 

References

  1. A Guide to the 2017 International Standards of Care for SMA. Available at: http://smauk.org.uk/international-standards-of-care-for-sma (Accessed: 14th May 2021)
     
  2. Mercuri E et al. (2018) Diagnosis and management of spinal muscular atrophy: Part 1: recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscul Disord 28: 103-115.
     
  3. Finkel RS et al. (2018) Diagnosis and management of spinal muscular atrophy: Part 2: Pulmonary and acute care; medications, supplements and immunizations; other organ systems; and ethics. Neuromuscul Disord 28: 197-207.
     
  4. Finkel RS et al. (2017) ENMC SMA Workshop Study Group. 218th ENMC International Workshop: Revisiting the consensus on standards of care in SMA Naarden, The Netherlands, 19-21 February 2016. Neuromuscul Disord 27 (6):596-605.
     
  5. Montes J et al. (2009) Clinical outcome measures in spinal muscular atrophyJ Child Neurol 24: 968-978.
     
  6. Mercuri E, et al. (2012) Childhood spinal muscular 
    atrophy: controversies and challenges. Lancet Neurol 11: 443-452.
     
  7. Tsirikos AI & Baker ADL (2006) Spinal muscular atrophy: classification, aetiology, and treatment of spinal deformity in children and adolescents. Curr Orthop 20: 430-445.
     
  8. Farrar MA et al. (2013) Pathophysiological insights derived by natural history and motor function of spinal muscular atrophyJ Pediatrics 162: 155-159.
     
  9. Gusset N et al. (2021) Understanding European patient expectations towards current therapeutic development in spinal muscular atrophy. Neuromuscul Disord 31(5): 419-430
     
  10. Zerres K et al. (1997) A collaborative study on the natural history of childhood and juvenile onset proximal spinal muscular atrophy (type II and III SMA): 569 patients. J Neurol Sci 146: 67-72
     
  11. Lunn MR & Wang CH (2008) Spinal muscular atrophy. Lancet, 371: 2120-2133.

We are grateful to the writers and reviewers who assist us in our information production. A list of who this includes may be requested from office@smauk.org.uk 

Whilst every effort is made to ensure that the information in this document is complete, correct and up to date, this cannot be guaranteed and SMA UK shall not be liable whatsoever for any damages incurred as a result of its use. SMA UK does not necessarily endorse the services provided by the organisations listed in our information sheets.

The information given in our publications is not intended to replace that provided by your healthcare team. Medical advice for any individual should always come from their own medical team.

If you have any feedback about this information, please do let us know at: office@smauk.org.uk