TREM2 and Nasu-Hakola disease: The main findings were then replicated in a second family composed of three patients, one carrying the TREM2 p.Q33X mutation and affected by NHD (referred to as NHD3) and parents heterozygous for TREM2 p.Q33X (referred to as HET1 and HET2) with an unremarkable clinical history for neurological disorders.