A similar trend was previously observed in a study of 298 patients with PD, where 3 of 6 carriers of both APOE-ε4 and GBA severe mutations progressed to dementia (HR 2.95; 95% CI 0.80 to 10.90).7 A faster decline in MMSE in GBA carriers with the APOE-ε4 allele was also recently shown in 100 Ashkenazi Jewish patients with DLB.43 The increased risk of cognitive impairment observed in carriers of both APOE-ε4 and GBA mutations is possibly due to the combination of neurodegenerative mechanisms mediated by these genotypes. The gene discussed is APOE; the disease is Lewy body dementia.