Muscular Dystrophy

Question 1

What is Muscular Dystrophy

Answer 1

inherited myopathic disorder with progressive muscle weakness and wasting

Question 2

What are the 2 types of Muscular Dystrophy

Answer 2

Duchenne

Becker

Question 3

How are most DMD cases inherited

Answer 3

Genetically, from mom carrying X chromosome
(only 1/3 of cases are spontaneous)
Rare in females

Question 4

How are most BMD cases inherited

Answer 4

genetically, from mom carrying X chromosome

rare in females

Question 5

What is the pathophys behind DMD

Answer 5

Genetic mutation on X chromosome (Xp21) causing LOSS of function= little-no Dystrophin

Question 6

What is the pathophys behind BMD

Answer 6

Genetic mutation on X chromosome (Xp21) causing reduced funciton= normal Dystrophin level, but it is altered

Question 7

What happens physiologically to muscles in MD

Answer 7

ongoing degeneration and regeneration

Skeletal muscles pseudohypertrophy (contracture) and eventually atrophy (weakness)

Question 8

What are Sx specific to DMD

Answer 8

Growth delay in 1st year
Cognitive impairment
Weakness between 2-3 y/o

Question 9

What muscle changes occur in DMD

Answer 9

proximal limb muscles before distal
LE before UE
Waddling (wheelchair by 12-15 y/o)
Gower’s sign (hand support when standing up)

Question 10

What respiratory changes occur in DMD

Answer 10

Impaired resp. function (need ventilator by 25) d/t Scoliosis and gradual weakening of respiratory muscles

Question 11

What cardiac changes occur in DMD

Answer 11

*Dilated Cardiomyopathy
cardiac abnormalities
-usually all during teen years

Question 12

What changes occur later in DMD progression

Answer 12

Urinary and bowel incontinence

Question 13

What sets BMD apart from DMD

Answer 13

In Becker’s, the growth delay and cognitive impairment are uncommon– Respiratory involvement is also less pronounced

Question 14

What muscular changes occur in Becker’s

Answer 14

Not involved until 5-15 y/o with milder, slower onset progression (can still make dystrophin, it’s just less effective)
No wheelchair until MUCH later (rare)

Question 15

What is the predominant feature in Becker’s MD

Answer 15

Cardiac involvement; because they are still able to move around, so they often stress the heart more

Question 16

When should you suspect Muscular Dystrophy

Answer 16

Delayed motor milestones in young kid w/ + FHx
Child not walking by 16-18 mo., Gower’s sign, toe walking, calf hypertrophy
Unexplained elevated ALT/AST

Question 17

What diagnostic studies can you get to help with Muscular Dystrophy Diagnosis

Answer 17

SrCr (50-100x higher in DMD, 5x higher in BMD) 
Genetic testing (Xp21) 
Muscle biopsy (DMD no dystrophin- BMD less dystrophin) 
\+/- DCM and respiratory function workup

Question 18

How can you treat Muscular Dystrophy

Answer 18

Prednisone (can delay wheelchair, but leads to Iatrogenic harm)
PT, Psych support
Surgery for muscle contractures/scoliosis
Ambulatory support
Cardioprotective meds
Ventilatory support