Making sense of genetic testing: The importance of a genetic diagnosis in DMD – Hear from our expert

Are you aware of the diagnostic techniques available for making a genetic diagnosis for children with suspected Duchenne muscular dystrophy (DMD)? Do you know about the critical importance of identifying the specific mutation?

Underscoring the importance of mutation types, Dr Aartsma-Rus discusses key steps for the early diagnosis of DMD. Mutations in the DMD gene eliminate or diminish dystrophin function, causing DMD and Becker muscular dystrophy (BMD; a milder inherited progressive muscle-wasting condition).1,2 As such, establishing a genetic diagnosis is critical for confirming diagnosis of DMD.

Watch now to find out more about the:

  • Disease continuum of DMD and the progressive loss of functionality  
  • Frequency and effect of different types of DMD-causing mutations on the dystrophin transcript
  • Distinctions between mutations found in BMD and DMD
  • Techniques available for making a genetic diagnosis for children with suspected DMD
  • Importance of having a specific genetic diagnosis in the context of disease prognosis and genetic counselling 

Prof. Dr. Annemieke Aartsma-Rus, Professor of Translational Genetics at Leiden University Medical Center (LUMC), the Netherlands, discusses the importance and methods of obtaining an early and accurate genetic diagnosis for DMD. She has played an important role in the development of antisense-mediated exon-skipping therapy for DMD during her PhD research at the Department of Human Genetics of the LUMC. In 2007, she became Group Leader of the Duchenne exon-skipping group. Since 2013, she has a visiting professorship at the Institute of Genetic Medicine of Newcastle University (UK).

Genetic testing is the only way to diagnose DMD. If you want to know more, click here.

Signs and symptoms of Duchenne muscular dystrophy (DMD)

Dr. Luca Bello discusses the importance of early diagnosis of DMD and how to recognise the early signs and symptoms (muscle weakness, not walking by 16-18 months, calf hypertrophy, cognitive and speech delay). If you suspect DMD, perform a creatine kinase (CK) test.

Click here to check the red flag signs and symptoms. If you suspect Duchenne muscular dystrophy, perform a creatine kinase (CK) test. Click here to learn more.

Reaching a Duchenne muscular dystrophy (DMD) diagnosis from an initial suspicion of the condition

Suspicion of DMD – next steps for diagnosis

Watch this video to hear from Dr. Luca Bello, Physician Neurologist from Padova, Italy discussing the diagnostic journey for a DMD patient. Starting with a creatine kinase (CK) test to the importance of an accurate diagnosis through genetic testing to enable the correct medical management options to be identified.

Don’t wait to investigate suspicions of Duchenne muscular dystrophy. Order a CK test, elevated CK levels should prompt referral to a neuromuscular specialist for further testing.

What are the early signs and symptoms of Duchenne muscular dystrophy?

The onset of symptoms occurs in childhood.1 Delayed motor milestones are the most noticeable signs in early childhood. Key symptoms can include:2
  • Delayed motor development2
  • Difficulty rising to stand or not walking well by 18 months1,3
  • Delayed speech and/or cognitive delay2

How a DMD child might rise from the floor: Gowers’ manoeuvre4–6

The difference in calf muscles of a healthy boy versus a boy with DMD

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Recognising red flag signs and symptoms

Developmental delay should trigger a creatine kinase (CK) test2,3

Carrier screening for Duchenne muscular dystrophy (DMD): why is it important and who is eligible?

Early detection means that women who are carrying the DMD mutation can:

  • Be offered genetic counselling, which can inform them about the risks of transmitting the mutated allele in future pregnancies2
  • Have the option of prenatal genetic testing2
  • Be made aware of alternative reproductive options, such as the use of donor eggs or human assisted reproduction with preimplantation genetic diagnosis (PGD)2
  • Undergo regular surveillance for cardiomyopathy from early adulthood5
  • Receive early cardiac treatment if heart involvement is detected3,4

Who is eligible for carrier analysis?

Family members of an individual with DMD should receive genetic counselling to establish who is at risk of being a carrier.1

Carrier genetic testing should be performed in female relatives of a boy or man who has been genetically confirmed to have DMD.1

Carrier testing may help reduce the transmission of Duchenne muscular dystrophy and improve outcomes for women at risk.1-4 Click here for the 2018 Duchenne Care Considerations.

The importance of early diagnosis

While there is no cure for Duchenne muscular dystrophy, studies have shown that early diagnosis and care can help slow DMD progression and minimise the risks and complications of the disease.1-5

This means that patients may:1,2,5-8

stairs

Remain ambulatory for longer

lungs

Preserve their pulmonary and cardiac function longer

Have a better quality of life

Live Longer

It also means:

  • Parents of patients can have earlier access to genetic counselling, which can assist with family planning2
  • It may be possible to enroll the child in research-based registries and clinical trials of investigational treatments2

Your role in detecting DMD has never been more important

Prompt intervention is critical to help delay disease progression and help preserve muscle function for as long as possible.

Early diagnosis and care can help slow Duchenne muscular dystrophy progression and minimize the risks of complications of the disease.
If you see signs and symptoms of Duchenne muscular dystrophy, order a creatine kinase (CK) test – click here to learn more

Genetic testing for Duchenne muscular dystrophy

Genetic testing is the only method for determining a patient’s specific mutation type.1,2 This is important because a specific genetic diagnosis may help identify medical management options and potential to enrol into clinical trials.2

Additionally, once a mutation is identified, female relatives can find out their carrier status. This is important for two main reasons:2

number 1

Female carriers can pass on Duchenne muscular dystrophy to their children

number 2

Female carriers need medical assessment and follow-up

A genetic diagnosis involves two types of tests

First-level testing1,3
  • The majority of mutations (~70%) are detected by multiplex ligation-dependent probe amplification (MLPA)
  • MLPA can detect both large deletions and large duplications in patients and carriers
Second-level testing1
  • If no mutation is found, gene sequencing should be performed
  • Only gene sequencing can definitely detect smaller mutation types. These mutations include point mutations (nonsense or missense), small deletions, and small duplications or insertions

How to accurately diagnose Duchenne muscular dystrophy1,2

Adapted from references 1, 4 and 5

Genetic testing is the only way to determine the specific mutation causing Duchenne muscular dystrophy and could help patients get on the right treatment pathway1,2

What is creatine kinase (CK)?

Creatine kinase (CK) is an enzyme found in skeletal muscle as well as in the heart, brain and other tissues. Increased amounts of CK are released into the blood when there is muscle damage.1 Elevated CK levels reflect muscle damage in patients with Duchenne muscular dystrophy, making it an important diagnostic marker for the condition.2

When to order a CK test

A CK test should be carried out if:

  • Examination and medical history suggest progressive muscle weakness1,3,4
  • A child has delayed motor function, such as not walking well or not able to rise to stand by 18 months1,3,5,6
  • A child shows developmental delay, including delays with mixed presentation (e.g. speech and cognition), and evaluation suggests a peripheral neuromuscular problem3
  • A child has a positive family history of Duchenne muscular dystrophy and suspicion of abnormal muscle function6
  • Blood tests reveal an unexplained increase in transaminases6

What the results mean1,6

IF CK IS ELEVATED
(Normal range is generally up to 250 U/L*)1
Refer to neuromuscular specialist for Duchenne muscular dystrophy gene testing6
IF CK IS NORMALDoes not rule out other neuromuscular disorders1

Developmental delay should trigger a CK test

Normal or mildly elevated CK levels do not rule out neuromuscular disease1

*The normal CK range is generally up to 250 U/L. Absolute values may differ between laboratories.1

Prompt CK testing can help to achieve the correct diagnosis and bring reassurance to families1,9

Genetic counselling offers many benefits for families living with Duchenne muscular dystrophy (DMD)

5 reasons to refer DMD families to a genetic counsellor:1-3

number 1

They provide education about DMD and its therapeutic options

number 2

They can coordinate diagnostic genetic testing

They can establish who is at risk of being a carrier and organise carrier genetic testing

They can discuss family planning options

They provide emotional counselling

International Care guidelines recommend that family members of an individual with Duchenne muscular dystrophy should receive genetic counselling to establish who is at risk of being a carrier.

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