Eighty-six myoclonus-dystonia (M-D) index patients from the Dutch national referral center underwent clinical and genetic evaluation in a study at University of Amsterdam, and other centers in the Netherlands and Belgium. Age of onset was 1 – 18 years in 48 (56%) and during adulthood in the remainder. Based on clinical examination, 24 cases were classified as definite M-D, 23 were probable, and 39 possible cases. According to previously published criteria, definite M-D had early onset and a positive family history. In the definite group, 50% carried an SGCE mutation; in the probable group, 4%; and in the possible cases, none had the mutation. 
COMMENT. Myoclonus-dystonia is a genetically heterogeneous movement disorder with autosomal dominant inheritance. The clinical manifestations are myoclonus and dystonia predominantly in the upper body, and in adults may respond to alcohol. A mild dystonia often presents as cervical dystonia or writer’s cramp; the myoclonus is rhythmic or arrhythmic, bilateral, asymmetric, involving mainly the proximal arms and axial muscles. The major gene locus maps to the epsilon-sarcoglycan gene (SGCE, DYT11) on chromosome 7q21-22. Various SGCE mutations are reported in several families and sporadic cases. In 50% cases of M-D, no mutation is identified.