Muscular dystrophy Flashcards
What is muscular dystrophy (MD)?
Muscular dystrophies are a group of inherited conditions that cause gradual wakening of the muscles, leading to increasing levels of disability. This is a progressive condition.
Some types eventually affect the heart or the muscles used when breathing, which can be life threatening.
What does MD cause?
This causes muscle weakness and wasting due to the degeneration of the muscle cells.
It typically starts with a particular group of muscles and then progresses to others.
What is the most common form of MD?
Duchenne muscular dystrophy.
It usually affects boys in early childhood and often shortens life expectancy as many with it die before or during their 30’s.
Other forms develop in later childhood, adulthood or middle age and can affect life expectancy.
What causes MD’s
MD’s are caused by mutations in the genes for muscle proteins, particularly dystrophin which strengthens the muscle fibres and protects them from injury as they contract and relax.
This causes changes to the muscle fibres and interferes with the muscles ability to function.
What can MD’s be classed as (gene mutations)?
You inherit an altered gene.
• Dominant inherited disorders: These are caused by dominant alleles, where the mutation can be inherited from ONE parent.
• Recessive inherited disorders: These are caused by recessive alleles, where the mutation must be inherited from BOTH parents.
• Sex-linked inherited disorders (like Duchenne): These are caused by sex-linked alleles, which are more common and more severe in males.
How do sex-linked inherited disorders work?
•Men have 1 x-chromosome and 1 y-chromosome.
• Women have 2 x-chromosomes.
Sex-linked disorders are caused by a mutation in the gene on the x-chromosomes.
As men only have 1 copy of each gene on the x-chromosome, so they will be affected by MD if one gene is mutated.
Women have 2 copies of the x-chromosome, so they’re less likely to develop MD, the healthy chromosome copy can compensate for the mutated one.
What is a gene mutation?
Changes in the base sequence of DNA.
What is a gene?
A sequence of bases in DNA that code for a polypeptide or protein.
What is duchenne MD?
The proximal muscles are affected (upper leg, pelvic, upper arms and shoulder area).
This is caused by sex-linked alleles and is therefore more common in men.
Symptoms typically appear between the ages of 1 and 2.
• Difficulty walking
• Difficulty standing
• Difficulty climbing stairs
• Behavioural or learning disabilities
• Muscles around the pelvis and thighs appear bulkier
What is becker MD?
The muscles in the hips, pelvis, thighs, shoulders and heart are affected.
Symptoms:
• Difficulty with sports
• Trouble climbing stairs
• Trouble walking quickly
• Trouble lifting
• Bigger calf muscles
• Learning disabilities
What is congenital MD?
This affects the muscles in the ankles, hips, knees and elbows.
What is myotonic MD?
This affects the muscles in the face, neck, fingers and ankles.
Symptoms:
• Muscle stiffness (falls, waddling, toe walking, muscle pain and big calves)
• Cataracts
• Excessive sleepiness
• Dysphagia (swallowing problems)
• Behavioural and LD’s
• Slow and irregular heart beat
What is Limb-girdle MD?
This affects the proximal muscles closest to the body, specifically the shoulders, upper arms, pelvic and thighs.
Symptoms:
• Muscle weakness in hips, thighs and arms
• Loss of muscle mass
• Back pain
• Heart palpitations
• irregular heartbeat
What is facioscapulohumeral MD?
This affects the muscles in the face, shoulder blades and upper arms.
Symptoms:
• Abdominal muscle weakness
• Hearing loss
• Non symmetrical face
What is emery-dreifuss MD
This affects the muscles in the upper arms, lower legs and hips.
