Dystonia is caused by incorrect signals from the brain to the affected body part but the causes for this are not yet fully understood. However, many cases of myoclonus dystonia are inherited, caused by mutations in a specific gene. The fault is found on the DYT11 gene (or SGCE gene). There is a 50% chance that a child will inherit the mutation if one parent has it. But inheriting the gene does not necessarily mean they will develop myoclonus dystonia.

  • ‘Maternal imprinting’ means the disorder may be passed down through families but only show in a grandmother and grandchildren. This happens when the gene is passed down by the mother and ‘switched off’ for her children. It is then ‘switched back on’ again when passed on by any male children to their offspring. E.g. There is a 50% chance that a son inherits the gene and if he does so then, for each of his children, a 50% chance that he will pass the gene on to them.
  • There are also a number of families with myoclonus dystonia but no DYT11 mutation, suggesting that there may be other genes that can cause this disorder and that more research needs to be done.
  • Sometimes a single case of myoclonus appears although no-one else in the family is affected. This is called a sporadic case. As sporadic cases of myoclonus dystonia have similar symptoms to familial cases it is possible that, even if the DYT11 mutation is not present, many of these will also have a genetic cause that has not yet been identified.