Myoclonus-dystonia is a movement disorder that typically affects the neck, torso, and arms. Individuals with this condition experience quick, involuntary muscle jerks or twitches (myoclonus). About half of individuals with myoclonus-dystonia develop dystonia, which is involuntary tensing of various muscles that causes unusual positioning. In myoclonus-dystonia, dystonia often affects one or both hands, causing writer's cramp, or the neck, causing the head to turn (torticollis).

Mutations in the SGCE gene cause 30 to 50 percent of cases of myoclonus-dystonia. The SGCE gene provides instructions for making a protein called epsilon (ε)-sarcoglycan, whose function is unknown. The ε-sarcoglycan protein is located within the outer membrane of cells in many tissues, but it is most abundant in nerve cells (neurons) in the brain and in muscle cells.

The prevalence of myoclonus-dystonia in Europe is estimated to be 1 in 500,000 individuals. Its prevalence elsewhere in the world is unknown.

In cases in which the genetic cause is known, myoclonus-dystonia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In cases in which the cause of the condition is unknown, the inheritance is unclear.

Published Date: October 01, 2017
Published By: National Institutes of Health