Previous studies had confirmed that TREM2 mutations increased the risk of Alzheimer's disease (AD) (Carmona et al., 2018), whereas the association of TREM2 mutations with PD remains controversial (Benitez and Cruchaga, 2013; Rayaprolu et al., 2013; Mengel et al., 2016). This evidence concerns the gene TREM2 and early-onset autosomal dominant Alzheimer disease.