It is shown that the presence of the APOE ε4 allele, altered miRNA expression and epigenetic dysregulationin the promoter region and exon 1 of TREM2, aswell as ANK1 hypermethylation and altered levelsof histone post-translational methylation leading to increased transcription ofTNFA, could variously explain increased levelsof peripheral and central inflammation found in AD. The gene discussed is APOE; the disease is Alzheimer disease.