TREM2 and Alzheimer disease: Common genetic risk factors of sporadic AD include genetic mutant in the ε4 allele of apolipoprotein E (APOE4) [246], sortilin-related receptor, L 1 (SORL1), triggering receptor expressed on myeloid cells 2 (TREM2), and ATP-binding cassette transporter 7 (ABCA7) (p.E709fs mutation [247]) [242].