The clinical phenotypic features of myoclonus-dystonia (M-D), including motor symptoms, psychiatric disorders, and neuropsychological deficits, were evaluated in 50 subjects from three M-D families examined at Mount Sinai School of Medicine, New York, and other centers. Each family had different truncating mutations in the SGCE gene on 7q21 chromosome, and one had an additional missense alteration in the DRD2 gene on llq23. The families had several motor features in common: symptoms began in the first or second decade and either myoclonus or dystonia or both involved the upper limbs, head, neck, or trunk. Psychiatric disorders, correlating with the motor symptoms, occurred in most patients and included depression, obsessive-compulsive disorder, and substance abuse, especially alcohol dependence. Whether the OCD and other psychiatric problems are specifically related to the M-D gene mutations or are secondary to the stress of the disease remains to be determined. Cognitive tests revealed impaired verbal learning and memory in one family, impaired memory in a second, and none in a third family. 
COMMENT. A plethora of articles on myoclonus-dystonia syndrome (MDS) are published in current literature. The locus for MDS is mapped to 7q21 region and llq23, and 7 different heterogeneous mutations in the gene for epsilon-sarcoglycan (SGCE) have been identified (see Ped Neur Briefs Oct 2002;16:78-79). The present article identifies 3 families with different mutations in the SGCE on 7q21, and one also with a missense alteration in the DRRD2 gene on llq23.
A novel locus for inherited myoclonus-dystonia on chromosome 18pll has been reported in 13 members of a large Canadian family, reported from the Ottawa Hospital, University of Ottawa, Canada. 
Clinical findings of a M-D family with two distinct mutations are reported . A novel deletion in the DYT1 gene on the maternal side and a missense change in the SGCE gene on the paternal side were found. The father of the index case carried the 7q21 missense alteration and had mild intermittent myoclonus beginning in early childhood. The index case and her brother had both mutations and they presented with myoclonus in early childhood. Dystonia developed later, and both patients had psychiatric disorders.
Autosomal dominant GTP-CH deficiency presenting as a dopa-responsive myoclonus-dystonia syndrome is reported from University of Rome, Italy . A 17-year-old boy presented with myoclonus and later developed dystonia and bradykinesia. The paternal grandfather and three relatives had M-D and resting or postural tremor. A missense mutation was found in the exon 6 of GCH-1 gene (K224R).
An editorial is provided by Furukawa Y and Rajput AH . Inherited M-D is a new term for “hereditary essential myoclonus” or “hereditary (alcohol-responsive) myoclonic dystonia”. Clinical features of inherited M-D are as follows: autosomal-dominant inheritance; onset in childhood or adolescence; myoclonus affecting neck, shoulders, and arms and dystonia manifested by torticollis and writer’s cramp; alcohol responsiveness; psychiatric problems; and a benign clinical course with normal life span. Locus heterogeneity includes 7q21 for the SGCE gene (10 families), 18pll (single family and unknown gene), and possibly, llq23 for DRD2. Pedigree analysis suggests maternal imprinting in genetically confirmed M-D families; this is responsible for reduced penetrance and non-expression of the trait when the disease is inherited maternally.