Dystrophinopathies
Overview
Duchenne muscular dystrophy
Becker muscular dystrophy
- X-linked recessive
- due to mutation in the gene encoding dystrophin, dystrophin gene on Xp21
- dystrophin is part of a large membrane associated protein in muscle which connects the muscle membrane to actin, part of the muscle cytoskeleton
- in Duchenne muscular dystrophy there is a frameshift mutation resulting in one or both of the binding sites are lost leading to a severe form
- in Becker muscular dystrophy there is a non-frameshift insertion in the dystrophin gene resulting in both binding sites being preserved leading to a milder form
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 muscular dystrophy
- develops after the age of 10 years
- intellectual impairment much less common
