Among the GCH1 variants identified by exome sequencing, two (Q110X and K224R) have been shown to cause GCH1 deficiency and DOPA-responsive dystonia in dominant pedigrees (Leuzzi et al., 2002; Saunders-Pullman et al., 2004) and two (V204I and M230I) have been reported in heterozygous sporadic or in recessive cases with DOPA-responsive dystonia (Segawa et al., 2004; Trender-Gerhard et al., 2009; Opladen et al., 2011). This evidence concerns the gene GCH1 and dopa-responsive dystonia.