22q11.2 deletion syndrome and schizophrenia

For decades, schizophrenia genetics has been a story of small effects from many variants. The 22q11.2 deletion is the most striking exception. People born with a missing chunk of chromosome 22 have lifetime psychosis risk roughly 25 times higher than the general population. The condition has helped researchers study schizophrenia from a different angle — what happens when a known, definable genetic event sets the trajectory.

What 22q11.2 deletion syndrome is

22q11.2 deletion syndrome (22q11DS) is caused by a small missing segment of chromosome 22, typically containing about 30–40 genes. It is also known by older names — DiGeorge syndrome, velocardiofacial syndrome, and Shprintzen syndrome — that emphasised different features. The deletion usually arises de novo (not inherited) but, once present, is autosomal dominant and can be passed to children.

The phenotype is highly variable. Common features include:

• Congenital heart defects, particularly conotruncal malformations
• Cleft palate or palate dysfunction
• Hypocalcaemia from hypoparathyroidism
• Immune deficiency, especially T-cell related
• Distinctive facial features, often subtle in adulthood
• Learning differences and intellectual disability across a wide range
• High rates of psychiatric conditions — anxiety, ADHD, autism spectrum, and most notably psychotic disorders

The International 22q11.2 Foundation and the NIH have detailed clinical resources. NORD also maintains a comprehensive overview at rarediseases.org.

The psychiatric picture

Multiple longitudinal studies — most notably from the International Consortium on Brain and Behavior in 22q11.2 Deletion Syndrome — have established the psychiatric trajectory:

• In childhood, ADHD, anxiety, and autism spectrum traits are common.
• In adolescence, attenuated psychotic symptoms — brief unusual perceptions, suspicious thoughts, magical thinking — appear in a substantial subset.
• In late adolescence and early adulthood, roughly 25% develop a full psychotic disorder, most commonly schizophrenia.

The 2014 paper by Schneider and colleagues in the American Journal of Psychiatry, drawing on the International Consortium, remains a key reference for these prevalence figures.

Why is the risk so high?

Several mechanistic threads have been pursued:

• COMT. The catechol-O-methyltransferase gene, which is deleted in 22q11DS, is involved in dopamine metabolism in the prefrontal cortex. Individuals with the deletion have lower COMT activity, which may affect dopamine handling.
• Mitochondrial genes. Several mitochondrial-related genes are within the deletion region.
• Neurodevelopmental signalling. Deleted genes including TBX1, DGCR8, and others contribute to early brain development.
• Cumulative burden. The deletion produces a small structural change in many systems, with the psychiatric phenotype likely emerging from interaction across pathways rather than any one gene.

No single gene in the deletion fully explains the schizophrenia risk, and animal models continue to clarify the picture.

Diagnosis and screening

22q11DS is diagnosed by genetic testing — historically with FISH (fluorescence in situ hybridisation), now more commonly with chromosomal microarray analysis (CMA) or multiplex ligation-dependent probe amplification (MLPA). Clinical guidelines from the American College of Medical Genetics and Genomics recommend testing in patients with congenital heart disease consistent with the syndrome, palate abnormalities, or other characteristic features. Some experts also recommend testing in adults with schizophrenia and any of the syndrome's somatic features.

How care is organised

Best-practice care is multidisciplinary. The 2015 international consensus guidelines for adults with 22q11.2 deletion syndrome recommend coordinated follow-up with cardiology, endocrinology, immunology, ENT, mental health, and primary care. Psychiatric care for someone with 22q11DS who develops schizophrenia uses standard antipsychotic and psychosocial treatment, but with two important caveats:

• Cardiac monitoring. Many people with 22q11DS have congenital heart disease, raising the importance of QT-monitoring and cardiac-safe antipsychotic choices. See our QT prolongation guide.
• Hypocalcaemia. Untreated hypocalcaemia can interact with seizure risk and antipsychotic side effects; routine calcium and PTH monitoring matters.

Implications for families

For families of children newly diagnosed with 22q11DS, the psychiatric statistics can feel frightening. Several points are worth holding alongside them:

• The 25% lifetime risk also means roughly 75% will not develop a psychotic disorder.
• Identifying the deletion early enables routine psychiatric monitoring and earlier intervention if symptoms emerge.
• Coordinated care across specialties — the 22q11.2 clinics at major academic centres — substantially improves outcomes across the syndrome.

Why 22q matters for schizophrenia research

22q11DS is one of the only contexts in which a defined genetic event reliably predicts a meaningful proportion of psychotic disorder. That makes it a uniquely valuable window into the neurobiology of schizophrenia. Longitudinal studies of children with 22q11DS have shown subtle changes in brain structure, cognition, and behaviour years before any psychotic symptoms emerge — informing the broader research effort on prevention and early identification. See our pieces on clinical high risk and preventing first-episode psychosis.

Resources

• International 22q11.2 Foundation
• NORD overview
• Major academic 22q11.2 clinics in Toronto, Philadelphia (Children's Hospital of Philadelphia), Utrecht, London, and elsewhere

This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.