Myotonia Congenita (Thomsen Disease and Becker Type)

Myotonia Congenita (Thomsen Disease and Becker Type)

What is myotonia congenita?

Myotonia Congenita is present from early childhood, but symptoms can be mild. Depending on the form of the disorder, symptoms and findings may become apparent from infancy to 2-3 years of age for Thomsen-type and between 4-12 years of age for Becker-type. Most individuals with myotonia congenita lead long, productive lives. Although muscle stiffness may interfere with everyday daily activities (i.e., walking, grasping, chewing, and swallowing), it is usually relieved with exercise. For an article about a professional boxer with myotonia congenita, see Despite Muscle Disease, 'Toy Tiger' Was an Awesome Fighting Machine.

There are two types of myotonia congenita: Becker-type myotonia is the most common form, while Thomsen disease is a very rare, relatively mild form.

What are the symptoms of myotonia congenita?

The main problems faced by people with this disease are delayed muscle relaxation and muscle stiffness, typically provoked by sudden movements after rest. See Signs and Symptoms.

What causes myotonia congenita?

This disease is caused by mutations in the gene for a chloride channel that’s necessary for shutting off the electrical excitation that causes muscle contraction.

The Becker type is inherited in an autosomal recessive pattern, meaning it is produced by defective genes contributed by both parents.

The Thomsen type is autosomal dominant, meaning it is produced by a defective gene contributed by one parent. For more, see Causes/Inheritance.

What is the progression of myotonia congenita?

Myotonia congenita has its onset in early to late childhood and does not progress. Someone who has myotonia congenita can lead a long, productive life, and can even excel at sports where strength is more important than agility.

For an article about a professional boxer with myotonia congenita, see Despite Muscle Disease, 'Toy Tiger' Was an Awesome Fighting Machine.

What is the status on research on myotonia congenita?

MDA supports ongoing research into the molecular bases of inherited myopathies and to find effective treatments. For more, see Research.