Muscular Dystrophy Flashcards
What is myotonic muscular dystrophy
most prevalent form of muscular dystrophy in ADULTS
autosomal dominant genetic mutation
Two distinct forms: Dystrophyia myotonica (DM1) and Proximal myotonic myopathy (DM2)
What is the cause of Dystophyia myotonica (DM1)
intronic mutation consistent of an unable expansion of a CTG repeat (DMPK) - shuts off myosin phosphatase
what is the cause of Proximal myotonic myopathy (DM2)
caused by a DNA expansion of CCTG repeat
How does DM1 present
“hatchet-shaped” face
frontal baldness
weakness of wrist and fingers
footdrop
proximal muscles LESS affected
dysarthria
dyphagia
ventilatory insufficiency
intellecutal impairment
hypersomnia
gonadal atrophy
cataracts
insulin resistance
how does DM2 present
mainly PROXIMAL muscles
cataracts
testicular atrophy
insulin resistance
constipation
hypersomnia
cognitive defects
How do you diagnose myotonic muscular dystrophy
history and physical
serum CK (normally to mildly elevated)
Histology
EMG
ECG
what is present on EMG and ECG for DM1
evidence of myotonia on EMG
first-degree heart block and more extensive conduction system involvement - complete heart block and sudden death can occur
heart failure can occur secondary to respiratory failure
How is myotonic Muscular dystrophy treated
symptomatic treatment
- cardiac pacemaker/implantable cardioverter defibrilator
- molded ankle-foot orthosis
- referral for sleep studies - eval for noninvasive respiratory support or pharmaceutical support (mondafinil (provigil))
drugs to supress myotonia (phenytoin)
What is Duchenne Muscular Dystrophy
PROGRESSIVE SYMMETRIC WEAKNESS AND WASTING OF MUSCLES= CHILDHOOD MD - MALES ONLY
x-linked recessive caused by mutations in the dystrophin gene - Females can be carriers
usually onset prior to 5 yo
what is the presentation of Duchenne MD
symmetric progressive PROXIMAL muscle weakness
-shoulder and hip are often affected
- gowers sign and calf muscle pseudohypertrophy
palpable muscle enlargement
cognitive deficits
loss of ability to walk
difficulty performing exercises (climbing, running, jumping, hopping)
How is DUchenne MD diagnosed
muscle enzymes (CPK) - increased 10x
Muscle biopsy - severely reduced or absent dystrophin necrotic muscle fibers with regeneration - fatty replacement of muscles
EMG - myopathy
EKG - cardiomyopathy - deep Q wave across pericardium
What is the treatment of Duchenne MD
prednisone/corticosteroids
passive muscle stretching
tenotomy
bracing
physiotherapy
mechanical assistive devices
avoid prolonged immobility
What are complications of Duchenne MD
respiratory failure
respiratory infections
aspiration pneumonia
acute gastric dilation
congestive heart failure
cardiac arrhythmia
What is the dystrophin gene
support structure to the muscle cells
What is the Gowers Sign
hands-and-knees position and then climbs to a stand by “walking” their hands progressively up their shins, knees, and thighs - sign of Duchennes MD
