GCH1 and Parkinson disease: Furthermore, we identified rare variants in parkinsonism and dystonia genes, including novel VPS13D homozygous variants in four cases, and heterozygous variants in PD8EB, KCNN2, CSF1R, THAP1, TOR1A, ANO3, GCH1, VPS16, KCDT17, KMT2B, and ATP1A3 genes.