APOE and early-onset autosomal dominant Alzheimer disease: The same study suggested that the cognitive decline observed in individuals who carry the APOE-ε4 allele, the strongest genetic risk factor for Alzheimer’s disease, in combination with the p.P522R PLCG2 variant, was slower and less pronounced compared to individuals who carried the APOE-ε4 allele without the protective p.P522R variant [10, 19].