Loss-of-function mutations in the X-linked endosomal Na+/H+ exchanger 6 (NHE6, encoded by the SLC9A6 gene) cause the neurological disorder Christianson syndrome (CS) (1, 2, 3, 4, 5, 6, 7, 8, 9, 10). Here, SLC9A6 is linked to Christianson syndrome.