It has been shown that specific point mutations in four genes that are involved in the lysosomal enzyme-targeting pathway (i.e., GNPTAB, GNPTG, NAGPA, and AP4E1) are linked to stuttering disorder (Han et al., 2019; Kang et al., 2010; Lee et al., 2011; Raza et al., 2015), in which they may contribute to up to 20% of the cases (Frigerio;Domingues and Drayna, 2017). This evidence concerns the gene NAGPA and stutter disorder.