Dopa responsive Dystonia (DRD) was first described in 1971 and typically begins at childhood with gait dysfunction caused by foot dystonia progressing to affect other extremities.
Dopa-responsive dystonia (DRD), also known as Segawa syndrome or hereditary progressive dystonia with diurnal fluctuation, is clinically characterized by the occurrence of simultaneous or late Parkinsonism and by an excellent response to treatment with low doses of L-dopa.
Similarly, there has been progress in our understanding of the genetic underpinnings of the "dystonia-plus" syndromes: dopa-responsive dystonia (DRD), myoclonus-dystonia (M-D), and rapid-onset dystonia-parkinsonism (RDP).
Hereditary Progressive Dystonia with marked diurnal fluctuation (HPD) is an autosomally dominantly inherited dystonia which is characterized by marked diurnal fluctuation of symptoms and by marked and sustained response to levodopa associated with mutations in guanosine triphosphate cyclohydrolase (GCH-1) deficiency gene.
Amantadine suppressed severe levodopa-induced choreic dyskinesia, which developed at initiation of levodopa therapy, in two siblings manifesting dystonia with motor delay phenotype of GTP cyclohydrolase I deficiency caused by compound heterozygous GCH1 mutations.
Autosomal dominantly inherited defects in the GTPCH gene (GCH1) cause a form of dystonia that is responsive to treatment with levodopa (dopa-responsive dystonia [DRD]).
Mutations of GCH result in reductions in GCH activity, BH4, TH activity, and dopamine, causing either recessively inherited GCH deficiency or dominantly inherited hereditary progressive dystonia [HPD; Segawa's disease; also called dopa-responsive dystonia (DRD)].4.
We conducted genomic DNA sequencing of the GCH gene in two patients (Cases 1 and 2) manifesting generalized dystonia responsive to levodopa and severe developmental motor delay.