Muscular Dystrophy

Question 1

What are muscular dystrophy disorders?

Answer 1

genetic defects that impair normal muscle fxn

Question 2

How is DMD inherited?

Answer 2

2/3 are inherited from mother carrying genetic mutation on X chromosome
(1/3 spontaneous)

Question 3

What is the mutation involved in DMD?

BMD?

Answer 3

DMD= Xp21 position -> loss of functional expression

BMD= Xp21 -> reduced functional expression

Question 4

What is the patho in muscular dystrophy?

Answer 4

Mutation ->
ongoing degeneration & regeneration of muscle fibers->
progressive breakdown of affected muscle

(starts as muscle hypertrophy, after years has atrophy)

Question 5

What are clinical manifestation of DMD?

Answer 5

• growth delay in 1st year of life
• cognitive impairment
• clinical onset of weakness begins 2-3 years old
• lower extremities before upper

Question 6

What is Gower’s sign, DMD?

Answer 6

using hand to support when arising from the ground (because legs are affected before upper extremities)

Question 7

How is respiratory fxn affected in DMD? What is needed?

Answer 7

scoliosis
gradual weakening of respiratory muscles

ventilator support by 25 years old

Question 8

How is the cardiac sx involved in DMD?

Answer 8

• primary dilated cardiomyopathy

- conduction abnormalities

Question 9

How does BMD compare to DMD?

Answer 9

BMD:

• growth delay is uncommon
• cognitive impairment is uncommon
• muscle involvement later in life (common to retain strength, contracture are less common)
• Cardiac involvement MORE predominant
• Less respiratory involvement

Question 10

What unexplained labs might you see in a pt w/ muscular dystrophy?

Answer 10

AST and ALT

Question 11

Dx studies for muscular dystrophy

Answer 11

-Serum creatine kinase
(DMD 50-100x nl, BMD 5x nl)
-genetic testing for Xp21 mutation

Others:

• EMG
• Muscle biopsy

Question 12

Tx of DMD and BMD

Answer 12

Prednisone 0.75 mg/kg once daily or on alternate days (can delay wheel chair dependence)