Community: Duchenne Muscular Dystrophy Flashcards
Describe Duchenne muscular distrophy
A genetic condition that affects the muscles, leading to progressive degeneration and weakness of specific muscle groups - often proximal muscles.
What causes DMD?
Genetic changes to the DMD gene that provides instructions for making the protein dystrophin
Where is the protein dystrophin found?
Skeletal muscles
Cardiac muscle
Small amounts in nerve cells in brain
What is the role of dystrophin?
Part of a complex that strengthens muscle fibres and prevents them from injury.
Acts as an anchor to connect cytoskeleton of muscle fibre to extracellular matrix ie important for cell stability
How is DMD inherited?
X linked recessive
Mainly males effected
Inherited from mother, who is a carrier or de novo mutation
At what age do symptoms typically occur?
Approx 3 to 4 years old
Why are the muscles usually firm in those affected?
When muscle breaks down it is replaced by fat and CT
What symptoms / signs are seen with DMD?
Proximal muscle weakness and atrophy that gets worse over time Delayed motor development - longer to learn to sit, stand or walk Delayed speech Have to mount stairs one by one Waddling gait Pseudo hypertrophy of calf muscles Progressive cardiomyopathy Scoliosis
What sign can be observed?
Gower’s sign - using arms to stand from squatting
By what age are most boys using a wheelchair?
Early teens
Why can breathing problems occur?
Weakness of diaphragm and muscles around lungs
What percentage have an intellectual impairment?
30%
Do not worsen as DMD progresses
Describe waddling gait
Walking on toes and arching back
How is it diagnosed?
Clinical examination
Family history
Blood tests
Genetic testing
What can blood indicate?
Raised CK - 40 x normal level
Raised ALT and AST
Why are female carriers usually not affected?
The have a second X chromosome from which the dystrophin protein produced
A small number of carriers may have a degree of muscle weakness = manifesting carriers
What should be offered after diagnosis?
Genetic advice (counselling) and testing for other family members at risk of being carriers should be provided
Is there a cure?
No
What treatment is available?
Physical therapy OT support Braces Corrective surgery Steroids to slow down degeneration Assisted ventilation Overnight CPAP - weakness of intercostal muscles can lead to nocturnal hypoxia (daytime irritability, headache, appetite loss)
What is the average life expectancy?
26
What percentage have learning difficulties?
1/3
Why typically causes death?
Respiratory failure or associated cardiomyopathy
