Skip to
  1. Homepage
  2. Rare diseases
  3. Search
Simple search

Simple search

*
(*) mandatory field





 

Other search option(s)

Thomsen and Becker disease

Orpha number ORPHA614
Synonym(s) Myotonia congenita
Prevalence 1-9 / 100 000
Inheritance
  • Autosomal recessive
  • Autosomal dominant
Age of onset Neonatal/infancy
ICD-10
  • G71.1
OMIM
UMLS
  • C0027127
  • C2936781
MeSH -
MedDRA
  • 10028655
  • 10043461
SNOMED CT -

Summary

Myotonia congenita is characterised by slow muscle relaxation associated with hyperexcitation of the muscle fibres. Prevalence is estimated at 1 between and 10/100,000. Onset occurs early in life and affected individuals are often identified by family members within the first few months after birth. The myotonia is unusual in that it is relieved by exercise (warm-up effect). The mode of transmission may be autosomal dominant (Thomsen myotonia) or autosomal recessive (Becker myotonia). Both forms of the disease are caused by loss of function mutations in the gene encoding the chloride channel (CLCN1) that plays a role in muscle cell repolarisation. The clinical diagnosis can easily be confirmed by electromyography (EMG), which reveals myotonic discharges in association with hyperexcitation of the muscle fibre membrane. Testing under exercise and cold stress allows detailed characterisation of the myotonia and helps orientate the molecular diagnosis. Identification of mutations in the chloride channel gene can be considered as diagnostic following a positive EMG under exercise and cold stress. Genetic counselling should be proposed and the results of the molecular analysis should be interpreted with care as the same mutations have been associated with both dominant and recessive modes of transmission depending on the family studied. Treatment revolves around sodium channel blocking agents such as mexiletine, carbamazepine or diphenylhydantoin.

Expert reviewer(s)

  • Pr Bertrand FONTAINE

(*) Required fields.

Attention: Only comments seeking to improve the quality and accuracy of information on the Orphanet website are accepted. For all other comments, please send your remarks via contact us. Only comments written in English can be processed.


Captcha image

Detailed information

Clinical genetics review
  • EN (2011)
Get Acrobat Reader
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.