GBA1 and Parkinson disease: Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra and α-synuclein pathology, manifesting clinically by motor symptoms such as tremor, rigidity, and bradykinesia, alongside cognitive and other non-motor impairments.1 While pathogenic mutations in LRRK2 and GBA are known to influence disease susceptibility and clinical course, there are likely additional genetic factors contributing to variability in disease manifestation.