Muscular Dystrophy

Question 1

What is muscular dystrophy?

Answer 1

progressive skeletal muscle degeneration due to atrophy, necrosis and pseudohypertrophy

• can affect other muscles later on in disease process
• atrophy is not from disuse
• pseudohypertrophy is due to deposition of adipose tissue

Question 2

There are different types of muscular dystrophy - how do they vary?

Answer 2

the different types of muscular dystrophy vary by the muscle groups affected, the age of onset, the rate of progression and the mode of inheritence

Question 3

Which type of muscular dystrophy is most common?

Answer 3

Duchenne muscular dystrophy

Question 4

Who is most affected by Duchenne muscular dystrophy?

Answer 4

men

Question 5

What is the etiology of Duchenne muscular dystrophy?

Answer 5

recessive, X-linked trait (mother is carrier to son)

• women can get it, but would require getting two defective X chromosomes

Question 6

What is the pathology of Duchenne muscular dystrophy?

Answer 6

• gene on short arm of X-chromosome codes for dystrophin, a protein on the membrane of muscle that attaches to/anchors contractile filaments
• if the protein is defective the filaments are not anchored properly and when used, they will be injured, will necrose with use
• muscle has poor ability to repair and regenerate
• causes more necrosis
• because the protein is on the membrane, permeability is affected
• calcium influx and enzyme (creatinine kinase) release
• fibrofatty connective tissue replaces muscle (attempt to compensate and regain size)

Question 7

What are the manifestations of Duchenne muscular dystrophy?

Answer 7

• asymptomatic until 2-3 years old
• progressive muscle weakness
• respiratory and cardiac muscles affected as disease progresses
• usually death from respiratory and cardiac complications

Question 8

How is Duchenne muscular dystrophy diagnosed?

Answer 8

• history
• observe voluntary movement (will be abnormal)
• serum CK
• muscle biopsy required for definitive diagnosis - will show pseudohypertrophy
• can also do a test to look for dystrophin in biopsy
• can also screen: for carrier, or do a prenatal screen of the fetus

Question 9

How is Duchenne muscular dystrophy treated?

Answer 9

• no cure
• supportive and symptomatic treatment
• increase comfort and function