We would like to note that the penetrance of the GCH-1 mutation is only 30 % supporting that the presence of a mutation does not guarantee clinical symptoms and a diagnosis of DRD [14], and that L-dopa response is so excellent in the most severely affected DRD cases after many years of treatment delay [25] that it is hard to imagine that mild clinical symptoms may be the only and residual symptoms. This evidence concerns the gene GCH1 and dystonia 5.