TREM2 and frontotemporal dementia: The importance of TREM2 in brain function has been illustrated by the autosomal recessive disorder Nasu‐Hakola disease (NHD) due to homozygous loss‐of‐function mutations in the TREM2 gene 11, 32, in which affected people develop a presenile frontotemporal dementia with sclerosing leukoencephalopathy and polycystic lipomembranous osteodysplasia.