Myotonic Dystrophy

Question 1

What is the most common adult muscular dystrophy?

Answer 1

Myotonic dystrophy

Question 2

What is the mutation seen in myotnic dystrophy?

Answer 2

Abnormal expansion of a DNA sequence in the DMPK gene –> leads to the production of toxic RNA molecules that interfere with normal cellular processes.

Question 3

What are the 2 types of myotonic dystrophy?

Answer 3

1) Type 1 (DM1) –> more common

2) Type 2 (DM2)

Question 4

What is the hallmark feature of myotonic dystrophy?

Answer 4

Delayed muscle relaxation following voluntary contraction or percussion (myotnia).

Question 5

Features of myotonic dystrophy?

Answer 5

1) Both DM1 and DM2 present with progressive muscular weakness:
- DM1 –> distal limb weakness predominantly affects the flexor muscles of the fingers, wrists, and ankles.
- DM2 –> proximal limb weakness affecting hip girdle muscles more than shoulder girdle muscles

2) Facial & bulbar weakness –> ptosis, facial diplegia, dysarthria, dysphagia or nasal regurgitation

3) Cardiac abnormalities

4) Frontal baldness in men

5) Atrophy of temporalis, masseters and facial muscle.

Question 6

What cardiac features may be seen in myotonic dystrophy?

Answer 6

1) Heart block

2) AF

3) Sudden cardiac death