ICD-11 definition : Thomsen and Becker disease are myotonic disorders characterised by slow muscle relaxation
associated with hyperexcitation of the muscle fibres occurring within the first few
months after birth. The myotonia is unusual in that it is relieved by exercise (warm-up
effect). Autosomal dominant myotonia congenita (Thomsen disease) is a non-dystrophic
muscle disorder caused by mutation in the gene encoding skeletal muscle chloride channel-1
(CLCN1). It is clinically characterized by muscle stiffness and an inability of the
muscle to relax after voluntary contraction. Autosomal recessive myotonia congenita
(Becker disease) is caused by mutation in the gene encoding skeletal muscle chloride
channel-1 (CLCN1). It is a non-dystrophic skeletal muscle disorder characterized by
muscle stiffness and an inability of the muscle to relax after voluntary contraction.
Most patients have symptom onset in the legs, which later progresses to the arms,
neck, and facial muscles. Many patients show marked hypertrophy of the lower limb
muscles. Transient muscle weakness is a characteristic feature.;
Thomsen and Becker disease are myotonic disorders characterised by slow muscle relaxation
associated with hyperexcitation of the muscle fibres occurring within the first few
months after birth. The myotonia is unusual in that it is relieved by exercise (warm-up
effect). Autosomal dominant myotonia congenita (Thomsen disease) is a non-dystrophic
muscle disorder caused by mutation in the gene encoding skeletal muscle chloride channel-1
(CLCN1). It is clinically characterized by muscle stiffness and an inability of the
muscle to relax after voluntary contraction. Autosomal recessive myotonia congenita
(Becker disease) is caused by mutation in the gene encoding skeletal muscle chloride
channel-1 (CLCN1). It is a non-dystrophic skeletal muscle disorder characterized by
muscle stiffness and an inability of the muscle to relax after voluntary contraction.
Most patients have symptom onset in the legs, which later progresses to the arms,
neck, and facial muscles. Many patients show marked hypertrophy of the lower limb
muscles. Transient muscle weakness is a characteristic feature.