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Condition report · Neurological

ZTTK Syndrome

Whole genome sequencing reads the SON gene for a change in one copy that causes ZTTK syndrome, a neurodevelopmental condition with intellectual disability, developmental delay and facial differences.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A rare neurodevelopmental disorder causing intellectual disability, developmental delay and a range of differences in brain, eyes, growth and other organs. It is caused by changes in one copy of the SON gene, usually arising new in the child.

ZTTK syndrome is a rare neurodevelopmental disorder that causes intellectual disability and developmental delay. Behaviour difficulties and seizures are reported in more than half of people. Facial differences are typical, and brain malformations, eye problems, short stature, feeding difficulties and kidney or genital differences are common. Less often there are heart, gut, immune or hearing problems.

The condition is caused by loss-of-function changes in one copy of SON, a gene involved in RNA splicing, which is a step in reading genetic instructions. The gene promotes the splicing of many genes that are essential for development. Almost all reported changes have arisen new in the affected person.

There is no treatment that directly addresses SON deficiency. Care is supportive, with developmental and educational support, treatment of seizures and movement disorders, and review of eyes, heart, kidneys and growth. Genetic counselling is recommended, and parental testing guides the recurrence risk, although most cases arise new.

The condition we analyse

Autosomal dominant

Caused by loss-of-function changes in one copy of SON, a gene involved in RNA splicing. Almost all reported changes have arisen de novo.

Signs and symptoms

Developmental delay and intellectual disability and facial differences are typical. Seizures and behavioural issues are reported in more than half of people. Brain malformations, eye problems, short stature, feeding difficulties and kidney or genital differences are common. Less often there are heart, gut, immune or hearing problems.

What a diagnosis changes

Developmental, feeding and educational support, with eye, heart, kidney and growth review and seizure treatment if needed. Most cases arise de novo, but genetic counselling and parental testing guide recurrence risk.

Genes analysed

Also known as

TOKIMS; Tokita-Kim syndrome; ZTTK multiple congenital anomalies-mental retardation syndrome; ZTTKS

MONDO:0014936OMIM 617140Orphanet 500150MedGen 934663Sources: [1][2][3]

Why whole genome sequencing

ZTTK syndrome is usually caused by a new change in one copy of SON, and the result helps direct the checks each person needs.

Supportive care for now

None of the available treatments directly addresses SON deficiency, so care focuses on the symptoms. Seizures, feeding, growth, eyes, heart and kidneys are monitored and treated as needed. Hearing aids may be helpful when hearing is reduced.

Counselling for families

Most cases arise new, but genetic counselling and parental testing guide the recurrence risk for other children. The result can also help the care team decide which organ reviews are needed.

References

  1. Mori M, Lemaire M, Raines G, Stone BS, Ahn EYE, 2025. Zhu-Tokita-Takenouchi-Kim Syndrome. GeneReviews
  2. Dingemans AJM, Truijen KMG, Kim JH, Alaçam Z, Faivre L, Collins KM et al., 2022. Establishing the phenotypic spectrum of ZTTK syndrome by analysis of 52 individuals with variants in SON. European journal of human genetics : EJHG
  3. Halliday BJ, Baynam G, Ewans L, Greenhalgh L, Leventer RJ, Pilz DT et al., 2022. Distinctive Brain Malformations in Zhu-Tokita-Takenouchi-Kim Syndrome. AJNR. American journal of neuroradiology

Other neurological conditions

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