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Acetazolamide-responsive myotonia

Disease definition

A form of potassium-aggravated myotonia (PAM) which shows dramatic improvement with the use of acetazolamide (ACZ).

ORPHA:99736

Classification level: Disorder
  • Synonym(s):
    • ACZ-responsive congenital myotonia
    • ACZ-responsive myotonia
    • Acetazolamide-responsive congenital myotonia
    • Myotonia-painful contractions syndrome
    • Painful congenital myotonia
    • Painful myotonia
  • Prevalence: 1-9 / 1 000 000
  • Inheritance: Autosomal dominant 
  • Age of onset: Childhood
  • ICD-10: G71.1
  • ICD-11: 8C71.2
  • OMIM: 608390
  • UMLS: C4275008
  • MeSH: -
  • GARD: -
  • MedDRA: -

Summary

Epidemiology

Prevalence is unknown.

Clinical description

Symptoms generally manifest during childhood (before 10 years old), with myotonia of the facial, limbs and/or intercostal muscles that is triggered by potassium ingestion, fasting and mildly by cold exposure and exercise. Muscle stiffness is generally painful. Additional clinical signs include generalized muscle hypertrophy, percussion myotonia of proximal upper extremity muscles, thenar eminence and tongue and myotonia in the eyelids. Paralysis or weakness is never observed.

Etiology

ACZ-responsive myotonia is a sodium muscle channelopathy due to missense mutations of the SCN4A gene, encoding the alpha subunit of the skeletal muscle voltage-gated sodium channel Nav1.4.

Genetic counseling

Transmission is autosomal dominant.

Management and treatment

Myotonia is dramatically improved with ACZ but when ACZ does not control myotonia or when side-effects occur such as kidney stone formation, mexiletine can be used as replacement therapy.

Expert reviewer(s):  Dr Savine VICART - Last update: October 2010

  A summary on this disease is available in Deutsch (2010) Español (2010) Français (2010) Nederlands (2010) Português (2010) Italiano (2011)

Detailed information

Guidelines

ERN produced/endorsed by ERN(s)   FSMR produced/endorsed by FSMR(s)

Additional information

Further information on this disease

Patient-centred resources for this disease

Research activities on this disease

Specialised Social Services

The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care by a qualified specialist and should not be used as a basis for diagnosis or treatment.