A case of myoclonus-dystonia diagnosed as Tourette Syndrome

Abstract

Myoclonus dystonia (M-D) is a rare movement disorder characterized by a combination of myoclonic jerks and mild dystonia typically beginning before age 20. M-D is caused by mutations in the SGCE gene in 36% of cases. We report a patient with genetically confirmed M-D who was initially diagnosed with Tourette syndrome (TS) for 15 years. Myoclonic jerks are distinguished from tics seen in Tourette syndrome in that they are not suppressed by conscious effort, are not preceded by an urge to carry out the movement, can interfere with voluntary movement, and are suppressed by alcohol intake. Conversely, tics seen in Tourette syndrome can be suppressed with conscious effort, are preceded by an urge to tic, often have a verbal component, do not normally interfere with voluntary movement, and are not reduced by alcohol. Although M-D is rare, it must be considered in patients with early onset myoclonus and dystonia, especially in cases with a positive family history.