Objective: To investigate the clinical characteristics and GCH I gene mutations in patients with dopa-responsive dystonia (DRD).
Methods: The clinical features of 3 families with 6 affected members and 8 sporadic cases were analyzed to determine the clinical characteristics, and 2 families with 4 affected members and 2 sporadic cases were screened for mutations of the GCH I gene.
Results: Age at onset was (10 +/- 3) years. Onset occurred earlier in female (9 +/- 4) years than in male (12 +/- 1) years. The initial symptom was a gait disorder, dystonia or tremor in most patients and nine patients (64%) presented with diurnal fluctuation. Thirteen patients (93%) were cured and one was improved after administration of low doses of levodopa for 3 months and no long-term side effects of levodopa had occurred. Two independent mutations were found in three patients. Gln161Pro, a new missense mutation, was found in a sporadic case, leading to a relatively severe phenotype. The two patients with mild phenotype in one family were found to have Lys224Arg mutation, as previously described.
Conclusions: DRD patients have diverse phenotypes and diurnal fluctuation is an important feature. They have dramatic and sustained response to levodopa. There may be a correlation between genotype and phenotype. The detection of GCH I mutations is helpful in early diagnosis of non-typical cases.