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Section 12 — Metabolic & Genetic Disorders Verify against local policy v1.0 · July 2026

Chapter 12.3 — Common Chromosomal Syndromes

Recognition and neonatal management of the common aneuploidies — trisomy 21, 18, 13, Turner (45,X), and 22q11.2 deletion — with an emphasis on associated malformation screening and compassionate, non-directive counseling — built on West Midlands Neonatal Guidelines 2025–28 and AAP genetics guidance

Educational guideline — verify locally. Confirm any suspected chromosomal diagnosis with appropriate genetic testing and Clinical Genetics input; counsel sensitively and non-directively. Management (including decisions around intervention in trisomy 13/18) is individualized with the family and specialists. Does not replace attending/genetics judgment.
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1. Overview

Overview

Chromosomal (aneuploidy and microdeletion) syndromes are recognized in the neonatal period through combinations of dysmorphic features and malformations. The neonatal team's role is to recognize the possibility, confirm the diagnosis with appropriate testing and Clinical Genetics, screen for the associated anomalies that determine early management (especially congenital heart disease), and support the family with compassionate, accurate, and non-directive counseling. Management is individualized — particularly for the severe trisomies 13 and 18, where care planning is shared between the family and the clinical team.

Why This Topic Matters

Early recognition guides urgent screening (e.g., cardiac disease) and appropriate, values-based care planning, and enables accurate, compassionate family communication. Missing an associated anomaly or counseling poorly causes avoidable harm.

2. Who This Guideline Applies To

Scope
  • Neonates with suspected or confirmed common chromosomal syndromes, or with dysmorphism/multiple anomalies.
  • Teams coordinating genetic confirmation, malformation screening, and family counseling.
  • Cross-references: genetic testing (12.2), dysmorphology (12.5), congenital heart disease (3.3), calcium disorders (4.8), and antenatal counseling (1.4).

3. Key Definitions

TermDefinition
AneuploidyAbnormal chromosome number (e.g., trisomy 21, 18, 13; monosomy X).
Trisomy 21Down syndrome — the commonest autosomal trisomy.
Trisomy 18 / 13Edwards / Patau syndrome — multiple severe malformations, high early mortality.
Turner syndrome (45,X)Monosomy X in females.
22q11.2 deletionDiGeorge/velocardiofacial syndrome — cardiac, hypocalcemia, immune features.

4. Trisomy 21 (Down Syndrome)

Recognition & Screening
  • Features: hypotonia, up-slanting palpebral fissures, flat facial profile/nasal bridge, epicanthic folds, single palmar (simian) crease, sandal gap, Brushfield spots.
  • Screen: echocardiogram (AVSD and other CHD), GI (duodenal atresia, Hirschsprung), FBC (transient abnormal myelopoiesis/leukemia risk), thyroid function, hearing, and eyes; feeding support.
  • Confirm with genetic testing; involve Clinical Genetics; provide up-to-date, balanced counseling and support/parent resources.

5. Trisomy 18 & Trisomy 13

Severe, Individualized Care
  • Trisomy 18 (Edwards): IUGR, clenched hands with overlapping fingers, rocker-bottom feet, micrognathia, cardiac and other malformations.
  • Trisomy 13 (Patau): holoprosencephaly-spectrum, midline defects (cleft lip/palate), microphthalmia, polydactyly, cardiac and CNS malformations.
  • Both carry high early mortality; care is individualized and shared with the family and specialists, ranging from comfort-focused care to selected interventions — approached compassionately and non-directively.
  • Confirm the diagnosis and screen major malformations to inform planning.

6. Turner Syndrome (45,X)

Features & Screening
  • Features: lymphedema of hands/feet, redundant nuchal skin/webbed neck, broad chest, sometimes detected antenatally (cystic hygroma/hydrops).
  • Screen: echocardiogram/aortic imaging (coarctation, bicuspid aortic valve) and renal ultrasound; later growth/endocrine follow-up (short stature, ovarian insufficiency).
  • Confirm karyotype; involve genetics and cardiology.

7. 22q11.2 Deletion (DiGeorge)

The CATCH-22 Cluster
  • Consider with conotruncal cardiac defects (e.g., tetralogy, interrupted aortic arch, truncus), hypocalcemia (hypoparathyroidism — see 4.8), thymic/immune deficiency, palatal anomalies, and dysmorphism.
  • Check calcium; assess immune status (avoid live vaccines/use irradiated products if significant immunodeficiency, per specialist); screen cardiac.
  • Confirm with targeted testing (FISH/microarray); involve genetics, cardiology, and immunology.

8. Management Algorithm

1
Recognize the pattern
Dysmorphism + malformations suggest a chromosomal syndrome; note the specific cluster.
2
Confirm & involve genetics
Appropriate genetic testing (rapid aneuploidy/FISH then karyotype/microarray — see 12.2); Clinical Genetics input.
3
Screen associated anomalies
Echocardiogram (all); syndrome-specific (GI/heme/thyroid in T21; aortic/renal in Turner; calcium/immune in 22q11.2).
4
Plan care with the family
Individualize (especially trisomy 13/18) — compassionate, non-directive, values-based shared decisions with specialists.
5
Support & follow-up
Feeding, developmental, and specialty follow-up; parent support/resources; genetic counseling for the family.
6
⚠ Do-not-miss
Congenital heart disease (all); duodenal atresia/TAM in T21; hypocalcemia/immune deficiency in 22q11.2; aortic coarctation in Turner.

9. Counseling

Compassionate & Non-Directive
  • Deliver the diagnosis sensitively, in a private setting, with both parents where possible; use accurate, up-to-date information and avoid outdated pessimism.
  • Be non-directive; respect the family's values, especially in decisions about intervention in severe trisomies.
  • Provide written information and parent-support resources; arrange genetic counseling and multidisciplinary follow-up.

10. Screening & Follow-up

SyndromeKey screening
Trisomy 21Echo; GI (duodenal atresia); FBC (TAM); thyroid; hearing; eyes; feeding/developmental follow-up.
Trisomy 18/13Confirm diagnosis; echo/major-malformation survey; individualized care planning.
Turner (45,X)Echo/aortic imaging (coarctation/BAV); renal ultrasound; growth/endocrine follow-up.
22q11.2 deletionCalcium; cardiac (conotruncal); immune status; palate; genetics/immunology.

11. Precautions

Safety Cautions
  • Confirm the diagnosis with genetic testing and Clinical Genetics before firm counseling — don't rely on appearance alone.
  • Always screen for congenital heart disease (echocardiogram) and the syndrome-specific anomalies.
  • Check calcium and immune status in suspected 22q11.2 deletion (irradiated blood products/avoid live vaccines if significant immunodeficiency).
  • Individualize trisomy 13/18 care with the family; counsel compassionately and non-directively.
  • Avoid outdated, overly pessimistic information; provide current resources.

12. Escalation & Family Support

Family-Centered Communication
  • "We think your baby may have a genetic condition. We'll confirm it with a specific test and a genetics specialist, and check the heart and other organs so we can care for your baby well."
  • "We'll give you accurate, up-to-date information and support, and make decisions together in a way that respects what matters to your family."

13. Key Pearls

High-Value Clinical Pearls
  • Confirm suspected chromosomal syndromes with genetic testing + Clinical Genetics; echocardiogram for all.
  • Trisomy 21: hypotonia/facies/single crease; screen cardiac (AVSD), duodenal atresia, TAM, thyroid, hearing, eyes.
  • Trisomy 18/13: severe malformations, high mortality — individualized, compassionate, non-directive care.
  • Turner (45,X): lymphedema/webbed neck; screen coarctation/BAV and renal.
  • 22q11.2 deletion: conotruncal CHD + hypocalcemia + immune deficiency — check calcium/immune status.
  • Counsel sensitively with current information; avoid outdated pessimism.

14. Common Mistakes to Avoid

MistakeWhy it harmsBetter practice
Diagnosing on appearance alone.Error; poor counseling.Confirm with testing + genetics.
Skipping the echocardiogram.Missed CHD.Echo for all suspected syndromes.
Missing hypocalcemia (22q11.2).Seizures/instability.Check calcium; immune status.
Directive/pessimistic counseling.Undermines shared decisions.Compassionate, non-directive, current info.
One-size-fits-all trisomy 13/18 care.Ignores family values.Individualize with family/specialists.

15. Board-Style High-Yield Summary

Key Takeaways
  • Confirm chromosomal syndromes with genetic testing + Clinical Genetics; screen for associated anomalies — echocardiogram for all.
  • Trisomy 21: hypotonia, characteristic facies, single palmar crease; screen cardiac (AVSD), duodenal atresia, TAM, thyroid, hearing, eyes.
  • Trisomy 18 (Edwards) and 13 (Patau): multiple severe malformations, high early mortality — individualized, compassionate, non-directive care.
  • Turner (45,X): lymphedema/webbed neck; screen coarctation/bicuspid aortic valve and renal anomalies.
  • 22q11.2 deletion (DiGeorge): conotruncal cardiac defects + hypocalcemia + immune deficiency — check calcium and immune status.
  • Counsel sensitively and non-directively with accurate, up-to-date information; arrange multidisciplinary follow-up.

16. References

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