The HR for progression to Hoehn and Yahr stage 3 is significantly greater in GBA mutation carriers with PD compared with non-carriers.11 There is also evidence to suggest that carriers of polymorphisms in GBA which are not generally considered to increase PD risk are at significantly increased risk of progression to Hoehn and Yahr stage 3.11 More recent data from a prospective longitudinal study suggest that GBA-associated patients with PD not only have more rapid progression of disease but also have reduced survival.12 This evidence concerns the gene GBA1 and Parkinson disease.