Dystrophinopathies

Question 1

What is the inheritance pattern of the dystrophinopathies?

Answer 1

X-linked recessive

Question 2

What causes the dystrophinopathies?

Answer 2

Mutation of the gene encoding for dystrophin on Xp21

Question 3

What type of mutation occurs in Duchenne muscular dystrophy?

Answer 3

Frameshift mutation resulting in one or both of the binding sites being lost - severe form

Question 4

What type of mutation occurs in Becker muscular dystrophy?

Answer 4

Non-frameshift insertion in the dystrophin gene resulting in both binding sites being preserved - milder form

Question 5

What are the signs of Duchenne muscular dystrophy?

Answer 5

Progressive proximal muscle weakness 5 yrs +
Calf pseudohypertrophy
Gower’s sign: walking up legs with arms
30% of patients have intellectual impairment

Poor prognosis

Question 6

What are the signs of Becker muscular dystrophy?

Answer 6

Onset 10 yrs +

Intellectual impairment less common