Syndrome of X linked intellectual disability, epilepsy, progressive brain atrophy and large head associated with SLC9A6 mutation.

SLC9A6 gene encodes for a sodium/hydrogen exchanger-6 protein mainly involved in endosomal trafficking and maintaining intraluminal pH. Loss of function mutations in SLC9A6 gene in children has been associated with Christianson syndrome and autism spectrum disorder. We describe a 3-year-old boy with intellectual disability, infantile-onset drug-refractory epilepsy, progressive brain atrophy and large head with a novel missense hemizygous mutation in exon 16 of the SLC9A6 gene on chromosome X. Presence of large head, early developmental regression and progressive cerebral atrophy expand the phenotypic spectrum of SLC9A6 mutations. Our case also highlights the importance of genetic testing in children with unexplained intellectual disability, epilepsy and neurodevelopmental impairments.