Genotype-Phenotype Correlation - Two Families with GCH1 Mutations

Dopa-responsive dystonia (DRD), attributed to GTP cyclohydrolase 1 (GCH1) mostly, is a clinically and genetically heterogeneous disorder. Our recent study have identified that phenotype may not be identical to genotype, even in the same family. One patient with parkinsonism was found to carry GCH1 mutation. Why phenotype is not correlated to genotype? Whether GCH1 is a risk factor for developing Parkinson’s disease (PD)? Further genetic and clinical studies are necessary to elucidate these questions.