Dystrophia Myotonica

Question 1

What is meant by “myopathic facies”?

Answer 1

Lifeless, lean and expressionless face

Bilateral ptosis and flaccid muscles around the mouth and eye due to facial weakness

If unsure about its presence, avoid presenting it!

Question 2

What are characteristic facial features of myotonic dystrophy?

Answer 2

Myopathic facies

Frontotemporal balding

Ptosis (bi- or unilateral)

Cataracts

Question 3

What other features of myotonic dystrophy would you notice on examination?

Answer 3

Distal wasting and weakness

Reduced/absent deep tendon reflexes

Question 4

What is myotonia?

Answer 4

Continued contraction of the muscle after voluntary contraction ceases, followed by imapired relaxation

E.g. Grip myotonia

Percussion myotonia- hypothenar eminency –> visible dent with slow filling.

Question 5

What conditions are associated with myotonic dystrophy?

Answer 5

Autoimmune:

• DM
• Goitre

Hypogonadism

Cardiac:

• Cardiomyopathy
• Valvular heart disease
• Arrhthymias- AF
• Conduction defects- pace makers

GI complications

Respiratory complications

Question 6

What is the genetic basis of myotonic dystrophy?

Answer 6

AD disease due to trinucleotide repeat on chromosome 19.

Question 7

What drugs can be used to help myotonia in these patients?

Answer 7

Phenytoin

Quinine

Procainamide

Question 8

What are other causes of myotonia?

Answer 8

Myotonia congenita:

• Thomsen’s disease - AD
• Becker’s disease (myotonia congenita) - AR, late onset