Given that the APOE ε4 allele has been linked to AD in a Brazilian cohort via co-segregation with a MAO-A polymorphism and an allelic variant of the serotonin transporter (Nishimura et al., 2005) and that a multiplex protein biochip for screening for AD –based on the ε4 allele and MAO-B– has been proposed (Veitinger et al., 2014), there is surprisingly very little published on the interaction between APOE risk alleles and MAO. This evidence concerns the gene MAOA and Alzheimer disease.