TREM2 and Alzheimer disease: The apolipoprotein E gene (APOE) has been identified as a major genetic risk factor causing sporadic cases of AD, while amyloid precursor protein (APP), presenilin 1/2 (PSEN1/2) genes, along with other co-morbidity factors, such as Triggering receptor expressed on myeloid cells 2 (TREM2), ATP- binding cassette transporter 1 (ABCA1), ATP-binding cassette transporter7 (ABCA7), Methylenetetrahydrofolate Dehydrogenase 1 (MTHFD1), Bridging Integrator 1 (BIN1) and gamma-secretase, are associated with Familial AD (Calero et al., 2015; Lanoiselée et al., 2017).