Dystonia

INDEX

In myoclonus–dystonia (DYT11), the features of two different movement disorders are combined.  Many kindreds with autosomal dominantly inherited myoclonus dystonia have mutations in the gene for epsilon sarcoglycan (SGCE). About 80 different mutations have been reported in SGCE, many of which are loss-of-function mutations due to frameshift, splice site, nonsense mutations, or deletions of whole exons or even the entire gene.

Mutation-positive patients present in childhood or adolescence, predominantly with myoclonus. The SGCE gene undergoes maternal genomic imprinting, so that only 10% of patients who inherit a mutated maternal gene will express the disorder, and a family history may therefore not be apparent. This impacts on genetic counselling since it is very unlikely that offspring who inherited the mutation from the mother will develop the disease because only the wildtype allele from the father will be expressed and the mutated, maternal allele will be inactive due to the imprinting mechanism8.

Furthermore, genetic heterogeneity in present, in that some patients with the clinical presentation of myoclonus-dystonia do not have SGCE gene mutations2.

Additionally, many carriers of SGCE mutations develop psychiatric features such as anxiety-related disorders and alcohol dependence.