BACKGROUND: Autosomal dominant dopa-responsive dystonia is commonly caused by 
mutations in the guanosine triphosphate cyclohydrolase-1 gene.
METHODS: We report a British family that has been followed for more than 20 
years in which no mutations were previously identified.
RESULTS: Reanalysis of this pedigree detected a duplication of guanosine 
triphosphate cyclohydrolase-1 exon 2 in affected family members. mRNA analysis 
showed a mutant transcript with a tandem exon 2 duplication. Four family members 
developed dopa-responsive dystonia, with onset in their late teens, and 
subsequently developed restless leg syndrome and migraine.
CONCLUSIONS: This is the first report of an intragenic guanosine triphosphate 
cyclohydrolase-1 duplication in a dopa-responsive dystonia family.