[Hereditary progressive dystonia with marked diurnal fluctuation (HPD)]

HPD is a clinical entity characterized by childhood-onset postural dystonia, which shows marked diurnal fluctuation (aggravation of symptoms towards evening and their alleviation in the morning after sleep), and dramatic and sustained response to levodopa without any adverse effects, such as wearing-off or dyskinesia. Since the first report by Segawa et al. (1971), many cases have been reported under the title HPD or related nomenclature. In this review, we describe details of clinical features and recent laboratory studies of HPD, to differentiate it from other disorders manifesting dystonia in childhood. It has been suggested that HPD has a genetically determined abnormality, being restricted to the terminals of the nigrostriatal dopaminergic neurons, which results in reduced dopamine content.