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Emergency: requires immediate attention
Myotonic dystrophy
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Myotonic dystrophy

Contributors: Andrea Wasilewski MD, Jamie Adams MD, Richard L. Barbano MD, PhD
Other Resources UpToDate PubMed


Myotonic dystrophy is an autosomal dominant, inherited, progressive disorder affecting the muscles. The disorder is characterized by muscle wasting, weakness, and myotonia (delayed relaxation of muscle). Wasting of the temporalis and masseter muscles combined with frontal balding results in its characteristic appearance. Patients have other abnormalities including cataracts, heart conduction defects, dysphagia, excessive daytime somnolence, and mild cognitive impairment.

Myotonic dystrophy type 1 has distal weakness, with myotonia prominent in the hands; type 2 has proximal muscle weakness (also called PROMM or proximal myotonic myopathy). The signs and symptoms of myotonic dystrophy typically manifest in the third or fourth decade, although they can occur at any age.

Congenital myotonic dystrophy can occur in neonates born to affected mothers. These children have a severe phenotype with prominent weakness, hypotonia, skeletal abnormalities, feeding difficulties, and respiratory distress at birth.


G71.11 – Myotonic muscular dystrophy

77956009 – Steinert myotonic dystrophy syndrome

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Differential Diagnosis & Pitfalls

  • Myotonia congenita
  • Paramyotonia congenita
  • Duchenne muscular dystrophy
  • Becker muscular dystrophy
  • Emery-Dreifuss muscular dystrophy
  • Limb-girdle muscular dystrophy
  • Fascioscapulohumeral muscular dystrophy
  • Oculopharyngeal muscular dystrophy
  • Spinal muscular atrophy
  • Glycogen storage disease type 2
  • Glycogen storage disease type 5
  • Carnitine deficiency
  • Carnitine palmitoyltransferase deficiency
  • Myasthenia gravis
  • Polymyositis
  • Stiff person syndrome
  • Tetanus

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Last Reviewed:10/18/2018
Last Updated:01/20/2022
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Emergency: requires immediate attention
Myotonic dystrophy
A medical illustration showing key findings of Myotonic dystrophy (Classic Type 1) : Distal muscle weakness, Dysarthria, AV conduction abnormality, Eyelid ptosis, Hypotonia, Cardiac dysrhythmia, Dysphagia, Asthenia, Myalgia, Cataract
Copyright © 2024 VisualDx®. All rights reserved.