11/14/24, 10\:54 AM Muscular Dystrophy

Muscular Dystrophy

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Muscular dystrophy\: group of genetic diseases with progressive weakness and muscle mass loss; caused by gene
mutations a
Common types\: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD).
Other types\: Emery-Dreifuss MD, limb-girdle MD, facioscapulohumeral MD.
Aetiology\: DMD and BMD are X-linked recessive; one-third of DMD cases due to spontaneous mutations. Other types have
autosomal dominant/recessive inheritance.
Typical features\: progressive proximal-to-distal weakness, delayed motor milestones, waddling gait, faltering growth,
fatigue, intellectual impairment, behavioural issues.
Examination
di
Initial investigation\: serum creatine kinase (CK) elevated from birth; peaks around age 2, declines with muscle wasting.
Diagnosis con
Management\: initial support and specialist referrals, early corticosteroids, vitamin D and calcium supplements,
physiotherapy, orthoses, serial casting. Later management includes electric wheelchair, counselling, orthopaedic input,
cardiac and respiratory surveillance.
Advanced planning\: ceilings of care discussions and early palliative care involvement.
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Introduction

Muscular dystrophy (MD) refers to a group of genetic diseases associated with progressive weakness and loss of muscle
mass. Mutations in genes responsible for the production of proteins key to healthy muscle development (e.g. dystrophin)
result in progressive muscle degeneration.
1
The two most common forms of MD are\:
Duchenne muscular dystrophy (DMD)
Becker muscular dystrophy (BMD)
Other less common types of MD include\:
Emery-Dreifuss muscular dystrophy (humeroperoneal MD - a
Limb-girdle muscular dystrophy
Facioscapulohumeral muscular dystrophy (a

Aetiology

DMD and BMD are classic examples of X-linked recessive conditions, meaning they mostly a
acting as carriers. However, one-third of DMD cases occur as a result of spontaneous mutations.
2
Other types of MD have di
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Autosomal dominant (AD)\: facioscapulohumeral, distal, ocular, oculopharyngeal MD
Autosomal recessive (AR)\: limb-girdle MD
Multiple forms of inheritance\: Emery-Dreifuss MD (can be X-linked recessive, AD or AR)

Clinical features

History

Typical presenting features of muscular dystrophy include\:
Progressive weakness\: starting proximally and moving distally with the lower limbs being a
limbs.
Delayed motor milestones\: typically the ability to walk independently.
Waddling gait
Other presenting features of muscular dystrophy may include\:
Faltering growth
Fatigue
Intellectual impairment (e.g. delayed speech milestones)
Behavioural issues\: attention de
Leg pain
In children with DMD, although histological and laboratory evidence of myopathy may be present from birth, the typical
clinical features of the condition (e.g. muscle weakness) do not usually become apparent until after the age of 2.
Children may
the creatine kinase level in children who cannot walk by 18 months of age to screen for MD. Once children with MD start
to walk, parents often describe them as 'clumsy' or 'falling all the time'
. A slow and ungainly run is a common presentation.
DMD patients usually become wheelchair users by the age of twelve. These children in particular tend to have evidence
of scoliosis and poor pulmonary function.
Death usually occurs in the second or third decade of life due to cardiac or pulmonary complications.
3
BMD is similar to DMD, but the manifestations of BMD typically develop later and are milder. Although muscle involvement
is less severe than in DMD, cardiac involvement is often a predominant feature of the presentation in BMD. Patients with
BMD tend to live past the fourth or
1

Clinical examination

Typical clinical
Weakness\: typically the proximal and distal leg muscles in the earlier phases of the disease.
Calf pseudohypertrophy\: due to the accumulation of connective tissue and fat replacing muscle tissue.
Waddling gait\: typically exacerbated when attempting to run.
Tip-toe walking\: occurs due to shortening of the Achilles tendon.
Gower's sign\: the child climbs up their legs when rising from the
Hypore
Loss of the arches of the feet (i.e.
Di
Clinical
3
Clinical
Winging of the scapula
Upper extremity weakness
Facial weakness
Clinical
Dysarthria
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Dysphagia
Clinical
Contractures a
Increased tone in the lumbar and paravertebral muscles.
Cardiac abnormalities such as

Investigations and diagnosis

The initial investigation used to screen for muscular dystrophy is serum creatine kinase (CK), an enzyme which leaks out of
damaged muscle cells. The level of CK is typically elevated from birth and peaks around the age of 2, after which it steadily
declines due to progressive muscle wasting. As a result, CK is not as reliable for screening in those who are already
wheelchair users.
De
Genetic analysis\: to identify known muscular dystrophy mutations.
Muscle biopsy\: to enable analysis of the dystrophin protein.
Findings on clinical examination
Other investigations which may be performed include\:
Electromyography\: myopathic changes are apparent including small polyphasic potentials.
ECG and echocardiography\: to screen for cardiomyopathy.
Lung function testing\: to identify restrictive lung disease secondary to muscular weakness.

Management

Initial management

After diagnosis, the family should be provided with appropriate information and support, including the o
for carrier status.
Other things to arrange after diagnosis include\:
Referral to any relevant specialists and/or multi-disciplinary teams (e.g. paediatric neurologist, cardiologist).
Immunisations\: including in

Early management

Early management encompasses the period in which the child is still walking.
Corticosteroids
Corticosteroids have been shown to prolong the child's ability to walk by 6-24 months. They also may help to slow the
progression of impaired respiratory function and cardiomyopathy.
5
Side e
Vitamin D and calcium supplements
Vitamin D and calcium supplements are often prescribed to enhance bone health.
Physiotherapy
Regular physiotherapy is essential to prevent the development of contractures.
Orthoses
Orthoses may be required to stabilise the knee, ankle and foot to prolong the child's ability to walk.
Serial casting of the ankles
Serial casting of the ankles is performed to prevent shortening of the Achilles tendon and the associated gait
abnormalities developing (e.g. tip-toe walking).

Later stage management

In the later stages of the disease, when the child is unable to walk, di
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Wheelchair
An electric wheelchair will be required to allow the child to continue to mobilise.
Counselling
Counselling may be required, particularly for adolescents.
Orthopaedic input
Orthopaedic input including orthotics and surgery for contractures and scoliosis.
Cardiac and respiratory surveillance
Cardiac and respiratory function will progressively deteriorate over the course of the disease and therefore e
surveillance is required to identify and treat problems early.
Respiratory surveillance and treatments options include\:
Monitoring of forced vital capacity, peak
Regular review by a respiratory physician
Low threshold for treating respiratory infections
Chest physiotherapy
Non-invasive ventilation (NIV)
Tracheostomy
Cardiovascular surveillance and treatments options include\:
Regular cardiology reviews to identify signs of cardiac failure (e.g. 6-monthly)
ECG and echocardiography to identify arrhythmias and impaired function
ACE inhibitors, diuretics and beta-blockers for heart failure
Advanced planning and palliative care
Given the progressive nature of the disease, it is important that discussions surrounding appropriate ceilings of care are
carried out in advance. Palliative care input should also be sought early in the terminal phase of the disease.

Further reading

If you're interested in learning more about neuromuscular disorders, take a look at the RCPCH e-learning module
developed by Dr Vanruiten, Consultant Paediatric Neurologist in the Great North Children's Hospital.

References

Up to Date. Duchenne and Becker muscular dystrophy. Clinical features and diagnosis. Available from\: [LINK].
Medscape. Population frequencies of inherited neuromuscular diseases - a world survey. Available from\: [LINK].
Emedicine Medscape. Muscular Dystrophy Treatment and Management. Available from\: [LINK].
Up to Date. Muscular Dystrophy, Duchenne and Becker muscular dystrophy\: Management and Prognosis. Available from\:
[LINK].
Manzur A, Kuntzer T, Pike M, et al. Glucocorticoid corticosteroids for Duchenne muscular dystrophy. Cochrane Database
Syst Rev. Available from\: [LINK].

Reviewer

Paediatric Consultant
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Contents

Introduction
Aetiology
Clinical features
Investigations and diagnosis
Management
Further reading
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