Subsequent clinical and genetic sequencing analyses revealed that heterozygous mutations in GBA1 are a major risk factor for the neurodegenerative diseases Parkinson's disease (PD) and dementia with Lewy bodies (DLB), with predicted frequencies of 7% to 12% in patient populations of both PD and DLB.13, 14, 15, 16. Here, GBA1 is linked to Lewy body dementia.