Muscular Dystrophy

Question 1

What is Duchenne muscular dystrophy?

Answer 1

-X-linked recessive inherited disorder in dystrophin gene required for normal muscular function)

Question 2

Features of DMD

Answer 2

-Progressive proximal muscle weakness from 5 years (pelvic)
-Calf pseudohypertrophy
-Gower’s sign (child uses arms to stand up from squatted position, proximal muscle weakness)
-30% intellectual impairment
-Associated with dilated cardiomyopathy
-Wheelchair bound by teens

Question 3

Investigation of DMD

Answer 3

-Raised creatinine kinase
-Genetic testing has now replaced muscle biopsy as the way to obtain a definitive diagnosis

Question 4

Management and prognosis of DMD

Answer 4

-Supportive, no effective treatment. Oral steroids: slow progression 2 years, creatinine supplementation?
-Most children cannot walk by the age of 12 years
-Patients typically survive to around the age of 25-30 years
-Associated with dilated cardiomyopathy

Question 5

Describe Becker muscular dystrophy

Answer 5

-X-linked recessive, non-frameshift
-Develops after age of 10 years, less severe DMD
-Intellectual impairment much less common

Question 6

Overview of myotonic dystrophy

Answer 6

-Inherited myopathy with features developing at 20-30. Autosomal dominant, trinucleotide repeat disorder
-Skeletal, cardiac, smooth muscle
-DM1: chromosome 19, distal weakness more prominent
-DM2: chromosome 3, proximal, severe congenital form not seen
PROLONGED MUSCLE CONTRACTION

General features
myotonic facies (long, ‘haggard’ appearance)
frontal balding
bilateral ptosis
cataracts
dysarthria

Other features
myotonia (tonic spasm of muscle)
weakness of arms and legs (distal initially)
mild mental impairment
diabetes mellitus
testicular atrophy
cardiac involvement: heart block, cardiomyopathy
dysphagia

Difficulty shaking someone’s hand