Intriguingly, the authors identified that a transition from stage 1 DAM to stage 2 DAM was dependent on triggering receptor expressed on myeloid cells 2 (Trem2) (52); homozygous loss-of-function mutations in this gene are known to cause autosomal recessive early-onset dementia [Nasu–Hakola disease and frontotemporal dementia (FTD)–like disease] (55–57). Here, TREM2 is linked to frontotemporal dementia.