DIAGNOSING SMA IN

INFANTS & CHILDREN

A doctor may first suspect spinal muscular atrophy (SMA) in a young child, when developmental milestones are not met, or in infants when they display signs of floppiness or decreased muscle tone. 

The characters shown are real patients and the required consent to use their stories has been obtained from the patients and families. Photographs are for illustrative purposes only.

CONFIRMING SPINAL MUSCULAR ATROPHY (SMA)

When SMA is suspected a paediatrician or paediatric neurologist may order genetic testing, which can help confirm or rule out the disease.

Diagnosing spinal muscular atrophy (SMA) in infants and young children is an important step towards identifying the most appropriate intervention. A recent survey of parents and doctors showed that the recognition of symptoms and finding a diagnosis required numerous visits to their paediatrician and specialists.1,2

Approximately 96% of individuals with a clinical diagnosis of SMA have a mutation in the SMN1 gene.

In order to confirm a diagnosis, a molecular genetic blood test must be performed to verify whether or not the child has a specific mutation in the SMN1 gene that causes SMA. This test is also referred to as an SMN gene deletion test. During this test, the increase in the number of the SMN2 gene should also be determined.3,4

The SMN gene deletion test is performed by several diagnostic laboratories. The results can be achieved in approximately 3 to 4 weeks, though this may vary by centre.5

A list of commonly used terms is available here

LISTEN TO BENJAMIN’S MUM PERSPECTIVE

“Our family doctor suggested […] ‘perhaps he’s a lazy baby’ - there were a lot of barriers in the language used.” 

– Benjamin’s mum

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LISTEN TO DOMINIC’S PARENTS PERSPECTIVE

“Your best chance of preventing disease progression is to have the condition diagnosed as soon as possible.” 

– Dominic’s dad

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The first thing a doctor may notice in a baby with SMA is floppiness or decreased muscle tone (hypotonia)3

Symptoms may include progressive muscle weakness, floppiness, and muscle wasting (atrophy). Muscle weakness is usually the same on both sides of the body.3

Each child may experience symptoms differently, and the disease is divided into types based on age of onset and functional ability. There is also a range of severity within each type, and as many as 25% of individuals may not have a precise type.6

Arriving at a diagnosis may take some medical detective work

  • Because each child shows signs and symptoms at different ages and with different severity, an initial diagnosis can be delayed.7
  • Children may receive other diagnostic tests, including additional genetic testing, electromyography, or a blood test to measure the level of creatine kinase — an enzyme that leaks out of deteriorating muscles.3
  • Unlike a genetic molecular blood test, these tests may not accurately confirm an SMA diagnosis, but they may be used to rule out other forms of muscle disease.3

Newborn screening

Although newborn screening is not yet standard practice, time to diagnosis is critical. Earlier diagnosis may help improve outcomes for children with spinal muscular atrophy.7

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The characters shown are real patients and the required consent to use their stories has been obtained from the patients and families. Photographs are for illustrative purposes only.

References

1. Qian Y, McGraw S, Henne J, Jarecki J, Hobby K, Yeh WS. Understanding the experiences and needs of individuals with spinal muscular atrophy and their parents: a qualitative study. BMC Neurol. 2015;15:217.

2. Lawton S, Hickerton C, Archibald AD, McClaren BJ, Metcalfe SA. A mixed methods exploration of families’ experiences of the diagnosis of childhood spinal muscular atrophy. Eur J Hum Genet. 2015;23(5):575–580.

3. Mercuri E, et al. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscl Disord. 2018;28(2):103–115.

4. Prior TW, Russman BS. Spinal muscular atrophy. NCBI Bookshelf Website. Available at: http://www.ncbi.nlm.nih.gov/books/NBK1352/. Updated November 14, 2013. Accessed April 15, 2016.

5. EGL Genetics. Congenital Hypotonia Panel: Spinal Muscular Atrophy Deletions, Prader-Willi/Angelman Syndrome Methylation, Myotonic Dystrophy, and Uniparental Disomy 14. Available at: http://geneticslab.emory.edu/tests/HY. Accessed January 9, 2017.

6. Lin CW, Kalb SJ, Yeh WS. Delay in diagnosis of spinal muscular atrophy: a systematic literature review. Pediatr Neurol. 2015;53(4):293–300.