Dystonia has been associated with mutations in genes encoding proteins critical for dopamine (DA) signaling, such as GTP-cyclohydrolase [34], tyrosine hydroxylase [35], as well as polymorphisms in the DA receptor subtype, D5R [64], and GNAL dystonia gene, which encodes G α olf, a central component for striatal responses to dopamine (DA) [36]. This evidence concerns the gene TH and Dystonia.