GCH1 and dystonia 5: Brain biochemical data from two of the four symptomatic cases with GTPCH-deficient DRD (Cases 1 and 2) and the asymptomatic GCH1 mutation carrier are available8, 38-42); consistent with the neuropathological findings (see above), striatal α-synuclein levels measured by quantitative blot immunolabeling39, 47, 48) were normal in Cases 1 and 2.