Homozygous loss-of-function mutations in TREM2 or DAP12 cause a rare and fatal disease known as Nasu-Hakola disease (NHD) or polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) which is characterized by an early-onset frontotemporal dementia-like phenotype and bone cysts [6, 7]. The gene discussed is TREM2; the disease is Nasu-Hakola disease.