Mutations in either TREM2 or DAP12 can cause polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL or Nasu-Hakola disease), which is also characterized by presenile dementia in homozygous carriers [7, 8]. The gene discussed is TREM2; the disease is Nasu-Hakola disease.