title: Phenocopies in a large GCH1 mutation positive family with dopa responsive dystonia: confusing the picture?
abstract: BACKGROUND
  Dopa responsive dystonia (DRD) is a disorder characterised by childhood onset dystonia but a wide range of clinical presentations has now been described.
  
  
  OBJECTIVE
  To study a large Canadian family with presumed DRD.
  
  
  METHODS
  The clinical features of the family were collected before molecular genetic mutational analysis.
  
  
  RESULTS
  All nine individuals in whom a clinical diagnosis of DRD was definite or probable were heterozygous for a GCH1 gene deletion. However, eight of nine possibly clinically affected members did not carry the GCH1 mutation.
  
  
  CONCLUSIONS
  Great care must be taken in diagnosing DRD even in families with the classic phenotype, because of potential phenocopies of the disease.
authors.affiliation: Parkinson's Disease and Movement Disorders Clinic, The Ottawa Hospital, Ottawa, Canada. dagrimes@ottawahospital.on.ca
authors.forename: D A
authors.initials: DA
authors.lastname: Grimes
authors.forename: C L
authors.initials: CL
authors.lastname: Barclay
authors.forename: J
authors.initials: J
authors.lastname: Duff
authors.forename: Y
authors.initials: Y
authors.lastname: Furukawa
authors.forename: A E
authors.initials: AE
authors.lastname: Lang
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D020821:Dystonic Disorders / Q000235:genetics* / Q000473:pathology; D005260:Female; D016368:Frameshift Mutation; D006136:GTP Cyclohydrolase / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction
chemical_list: D006136:GTP Cyclohydrolase