[MIM 300 243]

(X-linked intellectual disabilities -  craniofacial abnormalities - epilepsy - ophthalmoplegia - cerebellar atrophy; X-linked intellectual deficiency South Africa type)

Rare: reported in 6 families (less than 30 individuals, mostly of Norwegian origin). Mutation or deletion of the SLC9A6 gene on Xq26.3.  Very rare syndromic intellectual X-linked deficiency, characterized by microcephaly, severe developmental retardation or regression, hypotonia, abnormal movements, and early-onset seizures.

Male patients are severely affected: profound intellectual deficit, microcephaly, mutism, early epilepsy of variable types, developmental retardation, abnormal movements, and hypotonia. Other manifestations include ophthalmoplegia, truncal ataxia or of the walking, dystonia with stereotyped movements of the hands, frequent smiles with episodes of uncontrolled laughing, a autistic-like behavior disorder, an open mouth, major salivary incontinence and difficult swallowing, gastro-esophageal reflux and a slender habitus. It seems that the threshold of perception of painful stimuli is higher than normal. Usual death between 25 and 30 years of age.

MRI: hypoplasia or aplasia of the cerebellum, dilation of ventricles secondary to cerebral atrophy, thin corpus callosum.

Intellectual deficit has been reported in some women (carriers).

Similar symptomatology as in Angelman syndrome (see this term)

Anesthetic implications: 

swallowing disorders, epilepsy, gastro-esophageal reflux; high pain threshold.

References : 

Updated: October 2019