Recently the utility of α-synuclein RT-QuIC as an early diagnostic biomarker has been demonstrated in patients with isolated rapid eye movement sleep behaviour disorder (iRBD), which can be a prodromal stage of α-synucleinopathies including DLB, PD, and MSA: 97% of patients with iRBD who went on to develop clinically overt PD or DLB over a follow-up of 7 years had positive CSF α-synuclein RT-QuIC (Iranzo et al., 2021). This evidence concerns the gene SNCA and Lewy body dementia.