Features of patients with SLC9A6 mutations include mental retardation, microcephaly, truncal ataxia, grand mal epilepsy and lack of speech[OMIM #300243]. The clinical features of these patients suggest a similarity to Angelman syndrome, with developmental delay, ataxia, flexed arms, excessive drooling, happy demeanor with spontaneous smiling and laughter, as well as progressive microcephaly by two years of age. Most patients are found to have a slender body habitus, which differs from Angelman syndrome, where patients tend to become obese with age. Mutations in SLC9A6 are inherited in an X-linked pattern and result in clinical features in affected males and occasionally some mild features in carrier females.
Deletions and/or duplications of the SLC9A6 gene as causative of X-linked Angelman-like syndrome have been reported.