Child Health - Muscular Dystrophy

Question 1

Duchenne Muscular Dystrophy is caused by which mode of inheritance?

Answer 1

Autosomal X-linked recessive

Question 2

What are the main considerations when treating a child?

Answer 2

• Children are not small adults.
• They have unique physiology and different age ranges have different parameters.
  
  • Therefore, drug concentrations must be calculated per kg until the child is old enough.
• With respect to congenital problems - congenital disorders may take years to present.
• You can get A LOT of information from observing the child:
  
  • What do they do?
  • What don’t they do that you might expect them to?

Question 3

Which genetic defect causes Duchenne Muscular Dystrophy?

Answer 3

• DMD is caused by a defect in Xp21 Dystrophin gene.
• P = short arm of the chromosome.

Question 4

What is the disease process in a child with Duchenne Muscular Dystrophy?

Answer 4

• Destruction of skeletal muscle leading to progressive weakness.
• Pseudo-hypertrophy of the lower limb muscles - they look big but are actually being replaced with adipose tissue.
• Muscle wastage is progressive. Patients usually in wheelchair by early teens and death usually in 30s.
• The Dystrophin gene produces a protein that protects the mitochondria in the muscle. These mitochondria are destroyed in DMD so the muscles are subject to atrophy.

Question 5

Describe the presentation of a child with Duchenne Muscular Dystrophy.

Answer 5

• Positive Gower’s sign - typically presents with gross motor delay.
• Probably a delay in milestones - walking and hopping etc.
  
  • Not walking by 18 months is a huge red flag in any child.
• Pseudo-hypertrophy of the lower limb muscles - look big but are actually being replaced by adipose tissue.
• Speech - in clinic they can be nervous so ask parents how the speech is at home.

Question 6

What are the diagnostic tools used to identify Duchenne Muscular Dystrophy?

Answer 6

• Muscle cell biopsy will show changes in the muscle which can be useful for diagnosis.
• Ck (creatine kinase) is massively elevated in a child with DMD; this can be tested for in the blood.
• Definitive diagnosis comes from genetic testing.

Question 7

What are the treatments for a patient with Duchenne muscular dystrophy?

Answer 7

• The main treatment is exercise - physiotherapy to keep the muscles active.
• Steroids have been shown to help maintain muscle strength and prolong the period children can walk and stay healthy.
• BUT, the suppression of the normal steriod system in the body (controls immune system, puberty) causes problems.
  
  • Steroids need to be increased and sometimes testosterone must also be given.
• Gene / stem cell therapy will play a larger part in future.