Neurology · UKMLA & AKT
Becker muscular dystrophy
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- X-linked recessive neuromuscular disorder caused by mutations in the DMD gene (Xp21) - same gene as Duchenne muscular dystrophy (DMD)
- Prevalence: ~1 in 18,000 male births; 3-4x less common than DMD
- Reading frame rule distinguishes BMD from DMD: BMD = in-frame mutation → truncated but partially functional dystrophin produced; DMD = out-of-frame mutation → no functional dystrophin
- Most common mutations: large intragenic deletions (~65-70%), followed by duplications and point mutations
The in-frame vs out-of-frame distinction is the key molecular explanation for why BMD patients remain ambulatory into adulthood while DMD patients typically do not.
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