TREM2 and Nasu-Hakola disease: Current genome-wide association studies indicate loss of TREM2 function due to the presence of homozygous or heterozygous variants is highly associated with the progression of many neurodegenerative disorders, including AD, Nasu-Hakola disease (NHD), Frontotemporal dementia (FTD), and Parkinson's disease (PD)25–29.