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.