Muscular Dystrophies

Question 1

Epidemiology of DMD and BMD?

Answer 1

DMD 1 in 3600 live born boys

BMD 1 in 300000 for BMD

Question 2

Duchenne muscular dystrophy: (and Becker)
?inheritance
?defect
Most common hereditary neuromuscular disease

Answer 2

XLR (rarely AR). Xp21 = dystrophin in skeletal muscle (progressive weakness and prolif of conn tissue pseudohypertrophy of calves)
heart muscle (cardiomyopathy) and brain (mild intellectual imp).

Spontaneous 30%
Inherited 70%(maternal carrier)
Deletions most common (65%), duplications 7%, point mutations.

DMD - mutation disrupts reading frame = non functional protein = nonsense mutations

BMD - altered protein but preserved reading frame (mis-sense) = reduced amounts of semi functional protein