Duchenne Muscular Dystrophy Flashcards
What is Duchennes muscular dystrophy?
Duchennes muscular dystrophy is the most likely muscular dystrophy to turn up in your exams. It is caused by a defective gene for dystrophin on the X-chromosome. Dystrophin is a protein that helps hold muscles together at the cellular level. Given that boys have a single X-chromosome and girls have two, girls have a spare copy of the dystrophin gene. Female carriers of the condition do not usually notice any symptoms. This makes Duchennes muscular dystrophy an X-linked recessive condition. If a mother is a carrier (meaning she has one faulty gene) and she has a child, that child will have a 50% change of being a carrier if they female and 50% change of having the condition if they are male.
Boys with Duchennes present around 3 – 5 years with weakness in the muscles around their pelvis. The weakness tends to be progressive and eventually all muscles will be affected. They are usually wheelchair bound by the time they become a teenager. They have a life expectance of around 25 – 35 years with good management of the cardiac and respiratory complications.
Oral steroids have been shown to slow the progression of muscle weakness by as much as two years. Creatine supplementation can give a slight improvement in muscle strength. Genetic trials are ongoing.
What is Beckers muscular dystrophy?
Beckers muscular dystrophy is very similar to Duchennes, however the dystrophin gene is less severely affected and maintains some of its function. The clinical course is less predictable than Duchennes. Symptoms only start to appear around 8 – 12 years. Some patient require wheelchairs in their late 20s or 30s . Others able to walk with assistance into later adulthood. Management is similar to Duchennes.
What is myotonic dystrophy?
Myotonic dystrophy is a genetic disorder that usually presents in adulthood. Typical features are:
Progressive muscle weakness
Prolonged muscle contractions
Cataracts
Cardiac arrhythmias
What is limb girdle muscular dystrophy?
Limb-girdle muscular dystrophy usually presents in teenage years with progressive weakness around the limb girdles (hips and shoulders).
What is Gower’s sign?
Children with proximal muscle weakness use a specific technique to stand up from a lying position. This is called Gower’s sign.
To stand up, they get onto their hands and knees, then push their hips up and backwards like the “downward dog” yoga pose. They then shift their weight backwards and transfer their hands to their knees. Whilst keeping their legs mostly straight they walk their hands up their legs to get their upper body erect. This is because the muscles around the pelvis are not strong enough to get their upper body erect without the help of their arms.
