TREM2 and frontotemporal dementia: For example, TREM2 homozygous mutations, known to be the cause of Nasu-Hakola disease, were recently found to also cause frontotemporal dementia with no associated bone phenotypes (Guerreiro et al., 2013c); homozygous mutations in ATP13A2 (a gene known to cause Kufor-Rakeb) and GRN (where heterozygous mutations cause frontotemporal dementia) were identified in families with neuronal ceroid-lipofuscinosis (Bras et al., 2012a, Smith et al., 2012).