TREM2 and Nasu-Hakola disease: Cerebrospinal fluid sTREM2 levels were found to be significantly reduced in patients with dementia harboring NHD-associated TREM2 variants (Piccio et al., 2016), and reduced shedding of sTREM2 was observed in human kidney cell lines overexpressing NHD-associated mutant forms of TREM2 (Kleinberger et al., 2016).