Phân tích di truyền của một gia đình đã chứng minh liên kết với một khu vực khác trên 18p nhiễm sắc thể, gen này vẫn chưa được xác định. Khởi phát điển hình trong thập kỷ đầu tiên hoặc thứ hai. Myoclonus là tính năng nổi bật nhất, chủ yếu ảnh hưởng đến cánh tay, vai, cổ | DYSTONIA especially when transmitted maternally and with variable expression with males and females equally affected in most families. In many identified familial cases the disease is linked to a locus on chromosome 7q21 DYT11 and caused by mutations in the E-sarcoglycan gene. Genetic analysis of one family has demonstrated linkage to another region on chromosome 18p this gene has yet to be identified. Onset is typically in the first or second decade. Myoclonus is the most prominent feature primarily affecting the arms shoulders neck and trunk and less commonly affecting the face and legs. The myoclonic jerks can be triggered by voluntary movements action myoclonus and are particularly evident as overflow jerks . involving body regions not involved in the action per se . The myoclonic component may respond to alcohol. Dystonia usually torticollis and or writer s cramp occurs in some but not all affected patients and rarely is the only symptom of the disease. Psychiatric abnormalities including panic attacks and obsessive-compulsive behavior are frequently observed. RPD DYT12 RPD is a rare autosomal-dominant disorder characterized by the rapid onset or marked worsening of dystonia and parkinsonism usually over hours or days which then plateaus. Linkage analysis in the affected families points to a defect on the long arm of chromosome 19 and the gene which codes for Na K ATPase alpha 3 has been identified. This disorder commonly starts in adolescence. The dystonia can be focal segmental or generalized. Dysarthria grimacing bradyki-nesia postural instability and psychiatric disturbances are also described. There is little response to therapy including dopaminergics and anticholinergics. Paroxysmal Dyskinesias The inherited paroxysmal dyskinesias associated with gene loci DYT8 and DYT10 differ from the above-described genetic dystonias insofar as the dystonic features are clinically transient. The pathogen-esic mechanisms that underlie these fluctuating disorders .
