Muscular dystrophies

Question 1

Muscular dystrophies (MD) are a group of inherited genetic conditions that gradually cause the muscle atrophy and weakness, leading to an increasing level of disability. Is this a muscular or nerve issue?

Answer 1

• muscle issue

Question 2

There are lots of different types of muscular dystrophy. Of the following which is the most common?

1 - Duchennes muscular dystrophy
2 - Beckers muscular dystrophy
3 - Myotonic dystrophy
4 - Facioscapulohumeral muscular dystrophy
5 - Oculopharyngeal muscular dystrophy
6 - Limb-girdle muscular dystrophy
7 - Emery-Dreifuss muscular dystrophy

Answer 2

1 - Duchennes muscular dystrophy

Beckers muscular dystrophy is a less severe form of Duchennes muscular dystrophy, where there is some function of dystrophin

Question 3

Duchennes muscular dystrophy is the most common type of muscular dystrophy. What is the inheritance pattern of Duchennes muscular dystrophy?

1 - autosomal dominant
2 - x-linked dominant
3 - autosomal recessive
4 - x-linked recessive

Answer 3

4 - x-linked recessive

X relates to the X chromosome

• if male has this they will be affected as they only have one X chromosome
• if female has this they will be carrier as they have 2 X chromosomes, they will need to mutated X chromosomes to be affected

Question 4

What is the incidence of Duchennes muscular dystrophy?

1 - 150 cases per 100,000
2 - 15 cases per 100,000
3 - 1.5 cases per 100,000
4 - 0.15 cases per 100,000

Answer 4

4 - 0.15 cases per 100,000

Much more common in males due to X linked inheritance pattern

Question 5

What age is the peak incidence of Duchennes muscular dystrophy?

1 - 1-5
2 - 5-15
3 - 20-30
4 - >30

Answer 5

1 - 1-5

• 5-15 years = Beckers
• > 30 years = lower limb girdle

Question 6

What is typically affected in the mutation causing Duchennes muscular dystrophy?

1 - B-actin
2 - desmin
3 - dystrophin
4 - titin

Answer 6

3 - dystrophin

Dystrophin connects intracellular actin to the dystrophin associated protein complex (DAPC)
- DAPC attaches to the extracellular matrix.

Dystrophin essentially, acts as a stabiliser for the sarcolemma, without it the sarcolemma becomes damaged and weak

Question 7

Do children with Duchennes muscular dystrophy begin to walk at the same age as healthy children?

Answer 7

• no

They are delayed and have a waddling gait and increased falls

Most motor signs are delayed in Duchennes muscular dystrophy

Question 8

Children with Duchennes muscular dystrophy have a specific muscle group that undergoes pseudohypertrophy, which is really due to fat and fibrosis. Which muscle group is this?

1 - quadriceps
2 - hamstrings
3 - calves
4 - biceps

Answer 8

3 - calves

Question 9

Children with Duchennes muscular dystrophy can have difficulty moving from a lying to standing position, where they go onto all fours, then into downward dog and push backwards. What is this sign called?

1 - trellenberg sign
2 - gowers sign
3 - babinski reflex
4 - hoffmans sign

Answer 9

2 - gowers sign

Question 10

In Duchennes muscular dystrophy, their is muscle weakness. Is this distal to proximal or proximal to distal muscle weakness?

Answer 10

• proximal to distal muscle weakness

Question 11

Children with duchennes muscular dystrophy can have an intellectual disability. What % of patient experience this?

1 - 3%
2 - 13%
3 - 30%
4 - 65%

Answer 11

3 - 30%

Question 12

Which of the following is NOT a late symptom of duchennes muscular dystrophy?

1 - wheelchair bound/help
2 - gastrointestinal failure
3 - respiratory failure (weak diaphragm) 4 - scoliosis
5 - dilated cardiomyopathy and arrhythmias
6 - shortened lifespan.

Answer 12

2 - gastrointestinal failure

Question 13

Genetic testing through western blot or DNA testing is the gold standard diagnosis. However, which of the following is almost always raised and gives a good indicator of duchennes muscular dystrophy?

1 - creatinine kinase (CK)
2 - lactate dehydrogenase (LDH)
3 - alanine aminotransferase (ALT)
4 - aspartate aminotransferase (AST)

Answer 13

1 - creatinine kinase (CK)

All others can also be raised

Question 14

Duchennes muscular dystrophy cannot be cured. Which of the following can slow down muscle degeneration?

1 - zoledronic acid
2 - folic acid
3 - vitamin K
4 - glucocorticoids

Answer 14

4 - glucocorticoids

Prednisolone is drug of choice

BUT long term use can cause weight gain, osteoporosis and impaired glucose tolerance

Physical therapy can be helpful, but does not stop the process

Question 15

Steroid use can slow the degeneration in Duchennes muscular dystrophy. However, long term use can make the patient almost dependent. Stopping the steroids ab ruptly can cause which of the following?

1 - cushing syndrome
2 - addisonian crisis
3 - myxedema
4 - all of the above

Answer 15

4 - all of the above