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Duchenne muscular dystrophy is a severe, X-linked recessive neuromuscular disorder resulting in progressive degeneration of skeletal and cardiac muscle, caused by out-of-frame mutations in the DMD gene, leading to absence of dystrophin.

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DMD is the most common and severe form of muscular dystrophy in children, caused by mutations in the dystrophin gene (DMD) leading to absence of functional dystrophin protein.

https://youtu.be/DGOmN6rnsNk

https://youtu.be/gNdlsTdTRz4

https://www.youtube.com/watch?v=o1uhhpjmzkw

Etiopathogenesis

Gene	DMD (Xp21.2)
Protein	Dystrophin – links the muscle cytoskeleton to extracellular matrix via the dystrophin–glycoprotein complex
Mutation	Out-of-frame deletions, duplications, point mutations → absent dystrophin
Inheritance	X-linked recessive (affects males; females are carriers)

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Clinical Features

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DMD is characterized by early-onset, progressive muscle weakness, loss of ambulation in adolescence, and premature death usually due to cardiopulmonary complications.

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Age	Presentation
<5 years	Delayed walking, waddling gait, toe walking, falls
5–10 years	Gowers sign, calf pseudohypertrophy, proximal muscle weakness
>10 years	Loss of ambulation (usually by 12), progressive scoliosis
Teens–20s	Respiratory failure, dilated cardiomyopathy, arrhythmias
Cognitive	Mild intellectual disability (~1/3 cases)

Gowers sign: Child uses hands to “climb” up thighs to rise from floor, indicating proximal lower limb weakness.

Diagnosis

Laboratory:

Test	Findings
Serum CK	Markedly elevated (>10,000 U/L)
ALT/AST	Elevated even without liver disease
Genetic testing	First-line, detects mutation in DMD gene

Muscle Biopsy (if genetic test is inconclusive)

Absent dystrophin staining on immunohistochemistry (IHC)