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# Duchenne muscular dystrophy

An inherited disease of boys in which dystrophin is missing: muscles are damaged and weaken from childhood.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Gastrocnemius (inner head)](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/)
- [Gastrocnemius (outer head)](https://durgical.com/en/anatomy/lateral-head-of-gastrocnemius/)
- [Soleus](https://durgical.com/en/anatomy/soleus-muscle/)
- [Rectus femoris](https://durgical.com/en/anatomy/rectus-femoris-muscle/)
- [Vastus lateralis](https://durgical.com/en/anatomy/vastus-lateralis-muscle/)
- [Gluteus maximus](https://durgical.com/en/anatomy/gluteus-maximus-muscle/)
- [Diaphragm](https://durgical.com/en/anatomy/diaphragm/)
- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)

## In biochemistry

- [Creatine, phosphocreatine and creatinine](https://durgical.com/en/biochemistry/topics/creatine-phosphocreatine-and-creatinine/)
- [Creatinine](https://durgical.com/en/biochemistry/molecules/creatinine/)
- [Types of mutations](https://durgical.com/en/biochemistry/topics/types-of-mutations/)
- [Gene therapy](https://durgical.com/en/biochemistry/topics/gene-therapy/)

## In the clinical exam

- [Trendelenburg sign and gait](https://durgical.com/en/clinical-exam/trendelenburg-sign-and-gait/)

## In physiology

- [Sliding filaments and the cross-bridge cycle](https://durgical.com/en/physiology/sliding-filaments-and-the-cross-bridge-cycle/)
- [Motor units, recruitment and summation](https://durgical.com/en/physiology/motor-units-recruitment-and-summation/)
- [Muscle hypertrophy, atrophy and remodeling](https://durgical.com/en/physiology/muscle-hypertrophy-atrophy-and-remodeling/)

## Why it happens

- [Mendelian inheritance: autosomal dominant, recessive and X-linked](https://durgical.com/en/general-pathology/mendelian-inheritance-autosomal-dominant-recessive-and-x-linked/)
- [How a single gene causes disease: enzymes, receptors and structural proteins](https://durgical.com/en/general-pathology/how-a-single-gene-causes-disease-enzymes-receptors-and-structural-proteins/)

## What it is

An X-linked myopathy caused by DMD variants that abolish dystrophin, nearly always frameshifting deletions or nonsense mutations.

## Who gets it

Duchenne and Becker together affect 1 in 3,500 to 5,000 newborn males worldwide; Duchenne is the most common childhood muscular dystrophy. About a third of cases are new mutations. No national registry has been published in Colombia.

## Causes

- Variants in the DMD gene (Xp21), the largest human gene (79 exons)
- Deletions of one or more exons (≈ 65%), duplications (≈ 10%) and point mutations
- X-linked recessive inheritance; carrier mothers or a new mutation

## Risk factors

- Male sex
- Carrier mother
- Affected male relatives on the mother's side

## Pathophysiology

Dystrophin links the actin cytoskeleton to the membrane glycoprotein complex and the extracellular matrix; it acts as a shock absorber during contraction. If the deletion shifts the reading frame (frameshift), an early stop codon appears and no dystrophin is made (Duchenne). If the frame is kept, a shorter but working dystrophin is made (Becker, milder): this is the reading-frame rule. Without dystrophin the membrane tears with each contraction, calcium enters, proteases switch on and the fibre necroses; creatine kinase leaks into blood and muscle is replaced by fat and fibrous tissue (pseudohypertrophy).

## Classification

- Duchenne: no dystrophin, onset at 2–5 years
- Becker: reduced or shorter dystrophin, later onset and slower course
- Female carriers: sometimes mild weakness or cardiomyopathy

## Symptoms and signs

- Late walking, frequent falls, waddling gait and trouble running or climbing stairs
- Gowers sign: the child pushes on the legs with the hands to stand up from the floor
- Large, firm calves (pseudohypertrophy)
- Loss of walking around 10–13 years
- Scoliosis, contractures and, later, respiratory and heart failure
- Sometimes learning difficulties

## Red flags

- Breathlessness, morning headache or sleepiness (night-time hypoventilation)
- Palpitations, fainting or oedema (cardiomyopathy)
- Risk of a severe reaction to certain inhaled anaesthetics and succinylcholine

## Diagnosis

**Clinical**
A boy with proximal weakness, a Gowers sign and large calves.

**Tests**
Very high creatine kinase (tens of times normal); DMD genetic testing (MLPA for deletions and duplications, sequencing if negative); muscle biopsy showing absent dystrophin is kept for unclear cases.

**Imaging**
Muscle MRI shows the pattern of fatty infiltration; echocardiography and cardiac MRI follow the cardiomyopathy.

## Treatment

**Medical**
Daily or intermittent corticosteroids (prednisone, deflazacort or vamorolone): slow the loss of strength.

**Medical**
Exon-skipping antisense oligonucleotides for eligible deletions (e.g. exon 51 or 53) and stop-codon readthrough drugs for nonsense mutations, where available.

**Medical**
Early cardioprotection (ACE inhibitors or ARBs, beta-blockers, mineralocorticoid antagonists).

**Procedure**
Night-time non-invasive ventilation and cough assistance when lung function falls.

**Surgical**
Spinal fusion for progressive scoliosis and release of selected contractures.

**Rehabilitation**
Physiotherapy, stretching, night splints and wheelchair fitting.

## Complications

- Dilated cardiomyopathy and arrhythmias
- Restrictive respiratory failure
- Scoliosis
- Osteoporosis and fractures (worsened by corticosteroids)
- Rhabdomyolysis and hyperkalaemia with some anaesthetics

## Prognosis

With corticosteroids, ventilation and cardiac care, survival has moved from adolescence to the third or fourth decade; cardiomyopathy is now the main cause of death.

## Prevention

- Genetic counselling and carrier testing
- Prenatal or preimplantation diagnosis in affected families

## Test yourself

Think of the answer, then tap the question to see it.

## Why is Becker dystrophy milder than Duchenne?

In Becker the deletion keeps the reading frame and a short but working dystrophin is made; in Duchenne the frame shifts and there is no dystrophin.

## What is the Gowers sign?

The child gets up from the floor by pushing the hands on the legs because of pelvic-girdle weakness.

## Which first lab finding points to Duchenne?

A very high creatine kinase, tens of times the normal value.

## How does exon skipping work?

An antisense oligonucleotide makes the spliceosome skip an exon next to the deletion and restores the reading frame.

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## Related conditions

- [Heart failure](https://durgical.com/en/conditions/heart-failure/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Duchenne and Becker muscular dystrophy: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/duchenne-and-becker-muscular-dystrophy/) (MedlinePlus, US National Library of Medicine, 2026); [DMD gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/dmd/) (MedlinePlus, US National Library of Medicine, 2026); [Frameshift Mutation](https://www.genome.gov/genetics-glossary/Frameshift-Mutation) (National Human Genome Research Institute (NHGRI), 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Source: https://durgical.com/en/conditions/duchenne-muscular-dystrophy/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/duchenne-muscular-dystrophy/