Loss-of-function mutations in the TREM2 receptor or its adaptor, TYRO protein tyrosine kinase-binding protein (TYROBP), cause polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL; Online Mendelian Inheritance in Man # 221770), a recessive systemic disorder that presents with early-onset dementia (4) or familial frontotemporal dementia (5). This evidence concerns the gene TYROBP and Nasu-Hakola disease.