SLC9A6 and Cowden syndrome 1: The genetic basis of CS is loss-of-function (LoF) mutations in the X-linked gene SLC9A6, which encodes the endosomal Na+/H+ exchanger 6 (NHE6; Gilfillan et al., 2008; Garbern et al., 2010; Takahashi et al., 2011; Tzschach et al., 2011; Mignot et al., 2013; Riess et al., 2013; Pescosolido et al., 2014; Zanni et al., 2014; Masurel-Paulet et al., 2016).