**Duchenne muscular dystrophy (DMD)** is a severe, progressive genetic muscle‑wasting disease that mainly affects boys. It is caused by a mutation in the *DMD* gene, which leads to a lack of the protein **dystrophin**, resulting in ongoing damage and weakening of skeletal and heart muscles.
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### What it is
DMD is an **X‑linked recessive** muscular dystrophy, meaning it is inherited via the X chromosome and is far more common in males.
Without dystrophin, muscle cells are fragile and break down over time, gradually being replaced by fat and connective tissue.
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### Signs and symptoms
- Muscle weakness usually starts between **ages 2–5 years**, first in the hips, thighs, and pelvis.
- Children may have **delayed motor milestones**, frequent falls, difficulty running or climbing stairs, and a **waddling gait**.
- **Pseudohypertrophy** (enlarged calves due to fat replacing muscle) is a classic early sign.
- Later stages involve loss of walking (often by age scoliosis, muscle contractures, and **heart and respiratory muscle involvement***
### Cause and diagnosis
- DMD is caused by **mutations in the *DMD* gene** on the X chromosome that either eliminate or severely disrupt dystrophin.
- Diagnosis usually combines **elevated blood creatine kinase (CK)**, clinical features, and **genetic testing** (DNA or muscle biopsy for dystrophin).
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### Management and outlook
- There is **no cure**, but treatment focuses on **corticosteroids (glucocorticoids)**, **physical and respiratory therapy**, braces, wheelchairs, and monitoring of heart and lungs.
- Newer therapies include **exon‑skipping drugs** and **gene‑targeted treatments** that aim to restore some dystrophin production.
- Life expectancy has improved but is often into the **late teens or twenties**, mainly limited by **cardiomyopathy and respiratory failure**, with outcomes better in those diagnosed early and managed in specialized centres.
