• Both Duchenne and Becker muscular dystrophy are caused by mutations in a protein called dystrophin. In Duchenne muscular dystrophy, functioning dystrophin is completely absent in muscle, while in Becker muscular dystrophy, there is some dystrophin present, although not enough for completely normal muscle function.
• Both Duchenne and Becker's muscular dystrophy are inherited by X-linked recessive mechanisms, and so the vast majority of cases are males, with females being carriers.

Features

Duchenne muscular dystrophy:

• progressive proximal muscle weakness from 5 years
• calf pseudohypertrophy
• Gower's sign: child uses arms to stand up from a squatted position
• 30% of patients have intellectual impairment

Becker’s muscular dystrophy:

• Muscle wasting and weakness presents in late childhood - Usually become wheelchair-bound in their teens commonly survive into their thirties.

Investigation

• raised creatinine kinase
• genetic testing has now replaced muscle biopsy as the way to obtain a definitive diagnosis

Management

• is largely supportive as unfortunately there is currently no effective treatment