Types & Mutations
Different mutations in the dystrophin gene
Duchenne and Becker are caused by mutations (changes) within the dystrophin gene. A gene is made up of coding regions called exons, and the areas between exons are called introns. Making the dystrophin protein involves several steps. The first step is to remove the introns and fitting the exons together, 1 to 79, like puzzle pieces. If there is a missing (deletion) or extra (duplication) piece, the body can have difficulties making dystrophin.
Since the dystrophin gene is one of the largest genes in the body, it can have thousands of changes – or mutations that result in Duchenne or Becker. As some new therapies may only treat certain Duchenne and Becker mutations, it will be important to know which mutation the patient has.
The following table from PPMD USA shows the different types of mutations that can happen in the dystrophin gene, and how commonly the different mutations occur in people with Duchenne and Becker.
|Type of mutation
||How often mutation causes Duchenne
||How often mutation causes Becker
||60-70% of all cases
||80-85% of all cases
||10% of all cases
||5-10% of all cases
|Point mutations and other small changes (including ‘nonsense’ mutations)
||15-30% of all cases
||10-15% of all cases