GBA1 and Parkinson disease: Despite small numbers, NeuroX Known Mutation-PD samples harbouring single GD-associated GBA mutations appeared to have an excess of additional variants across all Mendelian genes studied (42.9%) (Supplementary Material, Table S3) as well as enrichment of additional ATP13A2 variants (14.3%) compared to No Known Mutation-PD cases (2.5%, P = 0.147) and controls (1.2%, P = 0.128) (Supplementary Material, Table S4).