Working on the latter project and another study regarding microglial involvement in AD using the APP‐PS1 mouse model (Audoy‐Remus et al., 2015), we recently uncovered the existence of a new myeloid cell phenotype, strikingly distinct from the other ones described so far at the ultrastructural level (referred here as “normal” microglia) (Graeber et al., 1988; Herndon, 1964; Mori and Leblond, 1969; Trapp et al., 2007; Tremblay et al., 2010a, 2012 among others). Here, PSEN1 is linked to Alzheimer disease.