We also note that the proband’s exaggerated startle reflex during the first 6 months of age (hyperekplexia), has previously been reported as a feature in association with SLC6A5-related disorders (Arribas-Gonzalez et al. 2015; Dreissen and Tijssen 2012; Michael Davis et al. 1993; Supplisson and Roux 2002), but not in association with NKH, suggesting this feature might be a common finding between GlyT1 and GlyT2 systems. This evidence concerns the gene SLC6A9 and hyperekplexia.