16p11.2 deletion syndrome
A small recurrent loss of chromosome 16 that raises the chance of speech delay, autism, obesity and a large head, with very variable effects.
What it is
A recurrent deletion of about 600 000 base pairs on the short arm of chromosome 16 (band p11.2), removing around 25 genes; it is one of the most common genomic causes of autism and developmental delay.
See it in 3D
Who gets it
About 3 in 10 000 people; found in roughly 1 in 100 people with autism spectrum disorder.
Causes
- Deletion arising from unequal recombination between flanking repeated segments (nonallelic homologous recombination)
- Often de novo; also inherited from a mildly affected or unaffected parent (autosomal dominant with reduced penetrance)
Risk factors
- A parent carrying the same deletion
Pathophysiology
Repeated DNA segments on either side of the region misalign at meiosis, and recombination between them deletes the segment between. Losing one copy of several dosage-sensitive genes there affects brain development and energy balance; the duplication of the same segment has roughly mirror-image effects (small head, low weight).
Classification
- Deletion (this condition)
- Reciprocal 16p11.2 duplication: microcephaly, low weight, developmental and psychiatric risks
Symptoms and signs
- Delayed speech and language, more than motor delay
- Learning difficulty or intellectual disability (often mild)
- Autism spectrum disorder or attention problems
- Obesity starting in childhood, with increased appetite
- Large head size
- Seizures in some
Diagnosis
- Clinical
- Suspected in a child with speech delay, autism or unexplained developmental delay, often with early obesity or macrocephaly.
- Tests
- Chromosomal microarray detects the deletion; testing both parents clarifies whether it is inherited and the recurrence risk.
- Imaging
- Brain MRI is usually normal or shows minor changes.
Treatment
- Rehabilitation
- Early speech, occupational and educational support.
- Lifestyle
- Early attention to diet and activity to prevent obesity.
- Medical
- Treatment of seizures and of associated behavioural or psychiatric conditions.
- Follow-up
- Follow-up of growth, weight and development.
Complications
- Obesity and its metabolic consequences
- Epilepsy
Prognosis
Very variable: some carriers have no obvious problems, others have significant developmental or behavioural difficulties.
Test yourself
Think of the answer, then tap the question to see it.
Which test detects the 16p11.2 deletion?
Chromosomal microarray; a karyotype is too coarse to see it.
Why can a parent carry the same deletion and be almost unaffected?
The deletion has incomplete penetrance and variable expressivity.
What do the deletion and the reciprocal duplication of 16p11.2 tend to do to head size and weight?
The deletion tends to cause a large head and obesity; the duplication a small head and low weight.
Connections
Educational information, not medical advice. For any symptom, see a health professional.
Sources: 16p11.2 deletion syndrome: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.