Diagnosis:
Clinical features: childhood onset of myotonia +muscle hypertrophy
There are multiple forms:
- Becker myotonia: Autosomal recessive
- Thomsen disease: (see appropriate section)
Genetics:
- Autosomal dominant
- Genetic analysis: chloride channel CLCN1 gene mutations on chromosome 7. Different mutations for each.
Muscle biopsy:
- Variation in fibre size. Rare centronucleation. Type 2A fibre hypertrophy. Type 2B fibres may be absent.
Related articles:
- Myopathy,
- Myotonia Congenita (Thomsen’s disease),