Muscular dystrophies Flashcards
1
Q
Signs of Duschenne’s MD on exam
A
- Gower’s sign
- Calf pseudohypertrophy
- Sparing of the bulbar muscles
- Inolvement of the myocardium and diaphragm
2
Q
Diagnosis of Duschenne’s and Becker’s muscular dystrophies
A
-
Supportive studies:
- Elevated serum CK
- EMG-NCS (showing intact nerve function and myopathy)
-
Definitive diagnosis
- Genetic testing
- Muscle biopsy (showing atophy, fatty infiltration)
- Note: Genetic testing is often pursued prior to muscle biopsy
3
Q
In DMD, most patients are affected by age ___ and need a wheelchair by age ___.
In BMD, most patients are affected by age ___ and need a wheelchair by age ___.
A
In DMD, most patients are affected by age 6 and need a wheelchair by age 12.
In BMD, most patients are affected by age 13 and need a wheelchair by age 30.
4
Q
1 cause of death in Duschenne’s muscular dystrophy
A
- Respiratory disease
* Note that most patients with DMD die by age 25
5
Q
Most patients with DMD have cardiomyopathy, however. . .
A
. . . heart failure is rare
6
Q
Treatment of muscular dystrophies
A
- Corticosteroids increase dystrophin expression and slow muscle degeneration
- Aggressive treatment of respiratory infections
7
Q
Cognition in muscular dystrophies
A
- DMD: Cognitive impairment with slightly lower IQ on average
- BMD: Mild to absent cognitive impairment (greater variance than DMD)
- Myotonic: Cognitive impairment with worsening attentional function over time but otherwise preserved cognition
8
Q
Myotonic dystrophy
A
- Autosomal dominant
- Due to nucleotide repeats
- Hallmark feature is myotonia: delayed muscle relaxation following contraction
- Classic sign is difficulty releasing a handshake
- Syndromic features often present
- Two types:
- Type I is caused by a DPMK mutation and affects distal muscles starting from birth, the juvenile period, or during adulthood.
- Type II is caused by a ZNF9 mutation and affects proximal muscles starting during adulthood.
