Muscular dystrophy (MD) refers to a group of nine genetic diseases that cause progressive weakness and degeneration of muscles used during voluntary movement; Duchenne Muscular Dystrophy is the most common form seen in children
Aetiology
X-linked recessive disorders (→ only boys affected) involving genes responsible for dystrophin, though one-third of cases are spontaneous mutations
Pathophysiology
Dystrophin is essential for cell membrane stability
In DMD there is an absence of dystrophin
In Becker’s dystrophy, dystrophin is present but levels are low - progresses much more slowly (but is less common)
Clinical features
Symptoms
Delay in motor development, some have more global delay
Signs
Onset of weakness 3-4 years - pelvic and shoulder girdles
Gower's sign: arms used to compensate for weakness of pelvic girdle muscles getting up from the floor
Toe walking
Exaggerated lumbar lordosis
Calf hypertrophy
In DMD, severe disability is typical by age 10
Becker’s muscular dystrophy is less severe than Duchenne and weakness only becomes apparent in young adults
