Muscular dystrophies

Last reviewed: March 2019

Last updated: March 2019

Summary

Duchenne muscular dystrophy (DMD) is highlighted as the most common and most rapidly progressive muscular dystrophy, with most patients losing the ability to walk by 12 years of age and requiring ventilatory support by 25 years of age.

Before the use of cardioprotective drugs and respiratory muscle aids, respiratory complications were responsible for 80% of deaths and cardiac complications were responsible for approximately 20%. Survival past 30 years of age is no longer rare, with 10% to 40% of patients with DMD surviving to age 40 in centers that use noninvasive means of respiratory support.

The development of acute respiratory failure, previously considered inevitable, can be preventable for most patients.

Severe scoliosis and the need for corrective surgery can be avoided, and the need for mechanical ventilation delayed, by early and aggressive use of corticosteroids.

With few exceptions, all generalized muscle disease can be managed using the principles for managing DMD.

Definition

Muscular dystrophies are progressive, generalized diseases of muscle, most often caused by defective or specifically absent glycoproteins (e.g., dystrophin) in the muscle membrane. All muscular dystrophies are characterized by ongoing degeneration and regeneration of muscle fibers. The most common and rapidly progressive muscular dystrophy is Duchenne muscular dystrophy (DMD). This is X-linked and diagnosed by the finding of absent dystrophin on muscle biopsy. Other X-linked muscular dystrophies include Becker muscular dystrophy (BMD), which is characterized by diminished quantity or quality of dystrophin in muscle biopsy specimens. BMD is a milder form of DMD. Diagnosis can be confirmed using multiplex ligation-dependent probe amplification or full sequencing of the dystrophin gene. This topic will mainly discuss DMD.

History and exam

Key diagnostic factors

family history of DMD
male sex
imbalance of lower limb strength
lower extremity musculotendinous contractures
delayed motor milestones
calf hypertrophy
ambulation difficulty and falls
diminished muscle tone and deep tendon reflexes
normal sensation

Full details

Other diagnostic factors

Gowers sign
toe walking
hypotonia
hyperactivity
urinary and bowel incontinence
mild to severe mental retardation

Full details

Risk factors

family history of DMD
male sex

Full details

Diagnostic investigations

1st investigations to order

serum creatine kinase (CK)
genetic testing

Full details

Investigations to consider

electromyogram (EMG)
muscle biopsy

Full details

Treatment algorithm

ACUTE

stage 1: ambulatory

stage 2: nonambulant

stage 3: ventilator-supported

Contributors

Authors VIEW ALL 

Pinki Munot, MD

Consultant Paediatric Neurologist

Great Ormond Street Hospital for Children

London

Disclosures

PM has received education and travel grants from PTC therapeutics (Ataluren) in 2016 for a conference.

Acknowledgements

Dr Pinki Munot would like to gratefully acknowledge Dr John R. Bach, Dr Aravindhan Veerapandiyan, and Dr Bilal Saulat, previous contributors to this topic. JRB, AV, and BS declare that they have no competing interests.

Peer reviewers VIEW ALL 

Lisa D. Hobson-Webb, MD

Assistant Professor of Medicine

Department of Medicine/Neurology

Duke University Medical Center

Durham

Disclosures

LDH-W declares that she has no competing interests.

Martin K. Childers, DO, PhD

Associate Professor Neurology and Regenerative Medicine

Wake Forest University Health Sciences

Winston-Salem

Disclosures

MKC declares that he has no competing interests.

Adnan Manzur, FRCPCH

Consultant Paediatric Neurologist

Great Ormond Street Hospital for Children NHS Trust

London

Disclosures

AM has been paid an honorarium for giving lectures at the Imperial College Educative Training Courses for GPs and post-graduate doctors. AM is the lead author of the Cochrane review of corticosteroids in Duchenne muscular dystrophy. He is also the Lead Clinician of the NorthStar Clinical Network for Management of Neuromuscular Disorders in the UK.

Richard W. Orrell, BSc, MD, FRCP

Senior Lecturer and Consultant Neurologist

Department of Clinical Neuroscience

UCL Institute of Neurology

London

Disclosures

RWO is an author of a reference cited in this topic.

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Muscular dystrophies

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

stage 1: ambulatory

stage 2: nonambulant

stage 3: ventilator-supported

Contributors

Authors VIEW ALL 

Pinki Munot, MD

Disclosures

Acknowledgements

Peer reviewers VIEW ALL 

Lisa D. Hobson-Webb, MD

Disclosures

Martin K. Childers, DO, PhD

Disclosures

Adnan Manzur, FRCPCH

Disclosures

Richard W. Orrell, BSc, MD, FRCP

Disclosures

Differentials

Guidelines

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