Caused by changes in SLC9A6, which encodes a protein that controls acidity inside cell compartments called endosomes. Males with one changed copy are affected; females who carry a change may be asymptomatic or have mild learning or behavioural difficulties.
Signs and symptoms
Boys have intellectual disability, often severe, with absent or very limited speech and seizures, usually starting in early childhood. A happy demeanour, hyperactivity, unsteady walking and small head size are common. Some people lose skills in later childhood, and eye movement problems or swallowing difficulties can occur.
What a diagnosis changes
Seizure treatment, physiotherapy, communication support and behavioural care, with monitoring of growth, feeding and walking. Genetic counselling and testing of the mother and female relatives clarify whether the change was inherited and the risk to future children.
Genes analysed
Also known as
Angelman-like syndrome X-linked; intellectual developmental disorder, X-linked syndromic, Christianson type; intellectual disability microcephaly epilepsy and ataxia syndrome; intellectual disability X-linked syndromic Christianson type; mental retardation, microcephaly, epilepsy, and ataxia syndrome; mental retardation, X-linked, syndromic, Christianson type; MRXS Christianson; MRXSCH; X-linked intellectual disability - craniofacial dysmorphism - epilepsy - ophthalmoplegia - cerebellar atrophy
