Myotonia congenita Becker

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Classification according to ICD-10
G71.1 Myotone Syndrome
Myotonia congenita, recessive (Becker)
ICD-10 online (WHO version 2019)

The myotonia congenita Becker is an inherited disorder of muscle function and is one of the so-called myopathies . It is named after the German doctor Peter Emil Becker . It can easily be confused with Becker muscular dystrophy , which was named after the same doctor, but represents a different clinical picture.

In contrast to Myotonia congenita Thomsen , Myotonia congenita Becker is an autosomal recessive inherited myotonia , which also usually begins in childhood. Autosomal recessive means that in this case both alleles of the CLCN1 gene on chromosome 7 must be damaged. The same gene is mutated as in Thomson , but in a different place. The prevalence is 1: 25,000.

The symptoms are similar to those of Myotonia congenita Thomsen, which means that contracted muscles relax only slowly, whereby the “warm-up effect” occurs again, the muscles function normally after repeated stress as long as they remain in motion. In general, the course of the disease is constant or the condition of the sick person only worsens very slowly. Compared to the dominantly inherited Thomsen form, the symptoms are rather mild. Life expectancy is not restricted. Membrane-stabilizing drugs such as mexiletine or phenytoin can improve the symptoms. On the other hand, depolarizing muscle relaxants are contraindicated; they can cause life-threatening conditions. The anesthetist should therefore be informed about this.

When inheriting the disease, it is important to distinguish between four possible constellations and the different probabilities of inheritance:

  1. Both parents are sick: 100%
  2. One parent falls ill, the other carrier: 50%
  3. Both parent carriers: 25%
  4. One parent falls ill, the other is healthy: 0%

literature