GCH1 and Parkinson disease: Based on the phenotypic heterogeneity, patients with P/LP variants in causative genes of other diseases, such as ATXN2 in spinocerebellar ataxia (SCA)8, GCH1 in dopamine responsive dystonia (DRD)9 or MAPT in frontotemporal lobar degeneration (FTLD)10, might present with PD-like symptoms in the early stage or even in the late disease course11 and might be clinically misdiagnosed as PD.