PREPL and myasthenic syndrome, congenital, 22: To date, only 10 patients with isolated PREPL deficiency (Jaeken et al., 2006; Régal et al., 2014, 2018; Laugwitz et al., 2018; Silva et al., 20186) and 21 HCS families (contiguous deletion, including the SLC3A1 and PREPL genes) have been reported (Clara and Lowenthal, 1966; Polgár, 2002; Font-Llitjós et al., 2005; Szeltner et al., 2005; García-Horsman et al., 2007; Martens et al., 2007; Boonen et al., 2011; Eggermann et al., 2012; Régal et al., 2012, 2014; Bartholdi et al., 2014; Wortmann et al., 2015).