Muscular Dystrophy

Question 1

how does muscular dystrophy occur?

Answer 1

inherited (x-linked recessive) gene

Question 2

how is muscular dystrophy characterized?

Answer 2

progressive

Question 3

what is the pathogenesis of muscular dystrophy?

Answer 3

absent dystrophin cannot protect complex
loss of complex = degrades muscle fibers

Question 4

which muscular dystrophy subtype is associated with the most severe clinical symptoms?

Answer 4

duchenne muscular dystrophy (DMD)

Question 5

which muscular dystrophy subtype is associated with a later onset and a milder clinical course?

Answer 5

becker muscular dystrophy (BMD)

Question 6

which muscular dystrophy subtype is associated damage to the heart and skeletal muscle is spared?

Answer 6

DMD-associated dilated cardiomyopathy

Question 7

what occurs to dystrophin in Duchenne muscular dystrophy (DMD)?

Answer 7

dystrophin levels are reduced or absent

Question 8

what occurs to dystrophin in Becker muscular dystrophy (BMD)?

Answer 8

dystrophin protein is altered

Question 9

what is the primary symptom in muscular dystrophy?

Answer 9

weakness

Question 10

which is affected first: proximal or distal limb muscles? upper or lower extremities?

Answer 10

proximal
lower

Question 11

using hands to push into an upright position when getting up from the floor

Answer 11

gower’s sign

Question 12

what presents in patients with Duchenne muscular dystrophy associated with dilated cardiomyopathy? (2)

Answer 12

conduction abnormalities
arrhythmias

Question 13

what 2 fracture locations are common?

Answer 13

arm and leg fractures

Question 14

what develops in nearly all patients with DMD? what can it lead to?

Answer 14

progressive scoliosis + weakness
acute respiratory failure

Question 15

what may be diminished or gone in DMD?

Answer 15

reflexes

Question 16

what is essential when muscular dystrophy is diagnosed?

Answer 16

genetic counseling for family

Question 17

what percentage of symptomatic female carries of a mutated dystrophin gene have an elevated serum CK?

Answer 17

70%

Question 18

how does elevated serum CK present in DMD?

Answer 18

10-20x the upper limit of normal

Question 19

how does elevated serum CK present in BMD/female carriers?

Answer 19

2-3x normal

Question 20

how early can molecular genetic testing be done?

Answer 20

12 weeks gestation

Question 21

what will be seen in a muscle biopsy to diagnose MD? (3)

Answer 21

degeneration
isolated opaque hypertrophic fibers
replacement of muscle by fat and connective tissue

Question 22

what is the clinical course of DMD? (2)

Answer 22

wheelchair bound by 12 yo
die in late teens from resp or cardio

Question 23

what is the clinical course of BMD? (2)

Answer 23

ambulatory into adult life
survive beyond 30 yo

Question 24

what is the mean age of death of a patient with BMD? what is the most common cause of death?

Answer 24

mid 40s
dilated cardiomyopathy

Question 25

what is the treatment for MD?

Answer 25

prednisone rehab w/ PT, OT, SLP vit D + calcium is needed

Question 26

what 2 diagnostics can be done to monitor MD?

Answer 26

echo or cardiac MRI

Question 27

what treatment should be started if evidence of ventricular dysfunction on cardiac imaging?

Answer 27

ACE inhibitor

Question 28

what treatment should be started if overt heart failure is present? (3)

Answer 28

diuretics digoxin +/- heart transplant

Question 29

what referral can be done if patient is in a wheelchair?

Answer 29

pulmonology