Hereditary dystonia is a chronic progressive disease with a wide variation in the severity of symptoms between cases. The age of onset varies depending on the genetic type. The dominant type starts at 6-14 years of age (range 140 years); the recessive type starts at an average age of 10 years, but also at other ages; the X-linked genetic type starts mostly at 25-45 years of age. The early symptoms of torsional dyskinesia begin with symptoms of dyskinesia in a restricted position, which is characterized by simultaneous and sustained contraction of the active and antagonistic muscles, resulting in impaired movement and fixation of the affected area in a specific position or posture. In the dominant form, the early manifestations are mostly abnormal postures of the mid-axis muscles of the body, especially the oblique neck, and in some cases, a twisted posture of the trunk or pelvic muscles is the main feature. In the recessive type, the first manifestation is abnormal gait or abnormal hand posture of one lower limb, inversion of foot position when walking, and difficulty in writing. In the early stage, the abnormal position or posture is intermittent or paroxysmal, triggered by voluntary movements, aggravated by emotional excitement or anxiety, and disappears after sleep. As the disease progresses, the abnormal postures appear frequently or even occur continuously without relief and do not disappear when falling asleep. The early restrictive symptoms gradually progress to the other side and become generalized dystonia including trunk and extremities. In severe spastic squint, the head is strongly rotated and tilted; in trunk muscle involvement, there is neck to back and trunk twisting along the long axis of the spine. The twisting action is due to persistent, unbalanced contraction of the active and antagonistic muscles, which can lead to limb deformation over time and severely impede voluntary movement. In some cases, the disease is mild, progresses slowly or stops progressing, and there may be only gait abnormalities, or only spastic slanting neck, or only writing spasms. Sometimes, oral-facial hypotonia is seen, causing difficulty in speech, articulation, swallowing and chewing. The disease is associated with normal intellectual development, no convulsive seizures, no cone fasciculation signs, and no sensory disturbances. The diagnosis is mainly based on clinical features. Central neurotransmitter tests may provide clues. A brain PET scan with fludopa reveals reduced uptake of dopamine by the nigrostriatal system. The diagnosis of the disease is based clinically on the presence of abnormal movements and posture in dystonia; normal perinatal period; no history of drug intoxication; no mental retardation, no pyramidal signs; family history; and exclusion of other causes of dystonia.