Armando Hasudungan
Biology and Medicine videos

Myotonic Dystrophy

Overview

Autosomal dominant disease characteristed by trinucelotide repeat of CTG

Signs and symptoms

Myotonia is defines as continued contraction of the muscle after voluntary contraction ceases.

Clinical features

  • Delayed relaxation after contraction – hand shake slow to release
  • Myotonic facies (expressionless, mouth open with a lean face)
    • Facial muscle weakness
    • Sternocledoid muscle weakness
  • Difficulty opening eyes after firm closure
  • Ptosis (often bilateral)
  • Cataracts
  • Balding
  • Distal muscle wasting and weakness – hands
  • Reduce reflexes
  • Foot drop
Remember Myotonic dystrophy type 2 has all the same features of the classic myotonic dystrophy with the difference being in proximal muscle wasting/weakness rather than distal.

Complications

  • Diabetes – polyuria, polydipsia
  • Cardiomyopathy – features of heart failure
  • Conduction abnormality – pacemaker
    • Supraventriular tachycardia (most common)
    • 1st degree heart block (40%)
  • Hypogonadism – gynacomastia and testicular atrophy
  • Goitre

 

Think What other disorders involve trinucleotide repeat

Complications

Endocrine complications

  • Type II diabetes melitius
  • Hypogonadism
  • Nodular thyroid enlargement

Cardiovascular complications

  • Resting ECG changes – everything prolonged (PR, QRS, QT)
  • Arrhythmia
    • Supraventricular tachycardia (most common)
    • VT
  • Conduction blocks
    • 1st (common)
    • 2nd
    • complete
  • Mitral valve prolapse
  • Cardiomyopathy

Gastrointestinal complications

  • Dysphagia
  • Reflux
  • Delayed gastric emptying
  • Malabsorption
  • Bacterial overgrowth
  • Megacolon

Respiratory complications

  • Hypoventilation – poor sleep
  • Respiratory failure follow anaesthesia
  • Recurrent pneumonia