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Duchenne and Becker muscle dystrophies

Duchenne muscle dystrophy:

It is the commonest type of dystrophy, XLR disorder, due to a defect in a

protein called dystrophin of the skeletal muscle, cardiac muscle and the brain.

Clinical picture:
Sex : usually male

Age : usually 3-5 years
Main characteristic features :

 Weakness : bilateral symmetrical , proximal > distal , with no sensory

manifestation

Weakness of the shoulder girdle muscles: unable to raise arm above the head,

winging of scapula (weak serratus anterior).

Weakness of pelvic girdle muscles:

- Waddling lordotic gait (weak gluteus medius and minimus )

- Difficulty climbing up stairs

- + ve gower sign.

➢ pseudohypertrophy of the calf muscles ,Deltoid and forearm.

Preserved muscles: hand muscles, extraocular muscle, urethral and anal

sphincter, diaphragm.

➢ Associated features :

- Cardiomyopathy → constant feature

- Mental subnormality → frank MR in 25% of cases

- Frequent respiratory infections and UTI

The course is gradually progressive :

- Most patients unable to walk at 12 years

- Death usually occurs by the end of second decade caused by respiratory

failure, heart failure.