duchenne muscular dystrophy (DMD)

Question 1

what is DMD

Answer 1

genetic disorder characterized by progressive muscle degeneration and weakness

Question 2

DMD cause

Answer 2

alterations of the protein dystrophin

Question 3

dystrophin purpose

Answer 3

• keeps muscle cells intact
• without it, cells are fragile and easily damaged

Question 4

DMD age onset

Answer 4

2-3 years old

Question 5

core symptoms of DMD

Answer 5

• muscle weakness
• progressive weakness + scoliosis –> impaired pulmonary function –> acute respiratory failure

Question 6

DMD symptoms

Answer 6

• core –> limb muscles
• lower –> upper muscles
• difficulties jumping, running, walking
• calf enlargement, waddling gait, lumbar lordosis
• later: heart and respiratory muscles

Question 7

DMD symptom range

Answer 7

mild skeletal weakness or cardiac involvement –> severe weakness or cardiac effects

Question 8

DMD life expectancy

Answer 8

into early 30s

Question 9

congenital myopathies histology classifications

Answer 9

• nemaline myopathy
• core myopathy
• centronuclear myopathy

Question 10

congential MD cause

Answer 10

• genetic disorder
• affects sarcolemma or membrane of muscle fibers holding the muscle together
• dystrophic and necrotic muscle fibers break down in stress due to structural failures

Question 11

common congenital MD name and symptoms

Answer 11

• COL6 (bethlem/ullrich)
• collagen disorder, difficulties bniding muscle fibers together
• muscle weakness, motor delay, hyperlaxed joints, rash (hyperkeratosis pylori), feeding difficulties
• develop keloid scarring often

Question 12

merosin negative MD associated difficulties

Answer 12

• white matter disorder
• cognitive and learning difficulties

Question 13

myotonic dystrophy

Answer 13

• weakness and myotonia (inability to relax a muscle after contraction)
• develop arrhythmia, cataracts, and respiratory/gut/endocrine involvement
• reduced fetal movements, failure to thrive, delays
• associated low IQ (50-90% < 80 IQ)

Question 14

why do people with DMD have big calves

Answer 14

• fatty replacement of scar tissue from fiber degeneration
• muscle fibers, sarcolemmas break down due to lack of dystrophin –> inflammation, degeneration
• muscle fibers build up and break down repeatedly
• progressive muscle fiber weakness, wasting, scarring, replacing with fatty scar tissue

Question 15

is DMD genetic or spontaneous at conception

Answer 15

• 2/3 X-linked from mom
• 1/3 inherit spontaneously at conception

Question 16

co-occurence of ASD/ADHD in DMD

Answer 16

30%

Question 17

milder version of DMD and why

Answer 17

• becker muscular dystrophy (B<D)
• dystrophin production absent in DMD and disrupted in BMD

Question 18

DMD mechanism of action

Answer 18

• little to no dystrophin production
• breakdown of muscle fibers and sarcolemma –> inflammation, degeneration
• muscle fiber builds up and breaks down repeatedly, fat replaces muscle tissues

Question 19

dystrophin purpose

Answer 19

shock absorber or scaffold for muscle fiber

Question 20

what is the largest gene (number of exons and why deletion is important)

Answer 20

• dystrophin, 79 exons
• DMD: out of frame deletion, sequence cannot continue
• BMD: in frame deletion, sequence can continue
• some deletions only occur in cardiac or cognitive areas, no other muscle involvement

Question 21

DMD treatments

Answer 21

• corticosteroids
• non-invasive ventilation
• ace inhibition

Question 22

treatment goal in MD

Answer 22

remediate underlying pathophysiology

Question 23

what do corticosteroids help with

Answer 23

• keep patients walking
• reduce contracture formation
• reduce scoliosis
• stabilize cardiac/respiratory issues
• prolong life expectancy

Question 24

ace inhibition purpose

Answer 24

• treat cardiac dysfunction
• improve life expectancy