McIlroy et al. reported that possession of the BuChE K allele constituted an increased risk for AD without any synergism with APOE ε4 allele distribution [41] whereas a recent study showed an overrepresentation of the BuChE K-variant in AD with reduced CSF BuChE activity in carriers of both the BuChE K-variant and the APOE ε4 allele [30]. The gene discussed is APOE; the disease is Alzheimer disease.