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Living with Trisomy 18

A chromosome condition with three copies of chromosome 18, affecting growth, development, and many organs.

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Understanding Trisomy 18

Trisomy 18 is a chromosome condition in which a person has three copies of chromosome 18 instead of the usual two.

Features include severe intellectual disability, low birth weight, a small, differently shaped head, a small jaw and mouth, clenched fists with overlapping fingers, and heart defects. Other organs can be affected too. GARD says most cases are not inherited and occur by chance. It starts during pregnancy.

Signs & symptoms

Symptoms vary from person to person. GARD lists these among the most common:

  • Severe intellectual disability
  • Small head (microcephaly)
  • Heart defects, such as a hole between the upper chambers
  • Clenched fists with overlapping fingers
  • Cleft palate
  • Acid reflux

Not everyone has every symptom. GARD's list comes from the Human Phenotype Ontology.

Diagnosis

  1. Talk with your doctor

    Share the symptoms you've noticed, when they started and your family health history. Notes and photos can help.

  2. See a specialist

    Specialists who may be involved include digestive system specialists, eye disease specialists, genetic specialists and kidney specialists.

  3. Ask which tests can help

    Your care team will decide which exams and tests can confirm the diagnosis.

Care & treatment

Care team
Digestive system specialists (gastroenterologists); Eye disease specialists (ophthalmologists); Genetic specialists (geneticists); Kidney specialists (nephrologists)
Expert care
Ask about multidisciplinary care centers for rare conditions
Treatment
GARD doesn't list specific treatments for this condition. Your care team will tailor care to your symptoms.
Research
Clinical trials and observational studies may be options. See the research section below.

General information, not medical advice. Your care team makes the decisions.

Everyday life

Living with a rare condition is easier with support.

  • Connect with Chromosome 18 Registry & Research Society and other patient organizations
  • Keep notes on symptoms, changes and questions for appointments
  • Ask about patient registries that help research
  • Look into financial aid and travel resources for care visits
Bring these questions to your next doctor visit
Which tests confirmed the extra chromosome 18?
Which specialists should be on our care team?
How are feeding and breathing supported?

Quick facts

Symptoms usually startduring Pregnancy and as a Newborn

It is caused by having three copies of chromosome 18 in the cells. GARD says most cases are not inherited and occur by chance.

GeneticKidneyGastrointestinal

Also known as: chromosome 18 duplication; complete trisomy 18 syndrome; e3 trisomy; edwards syndrome; trisomy type 18

Patient organizations

Source: NIH GARD · Trisomy 18GARD ID 6321 · GARD page updated September 2026 · Plain-language summary by Know Rare; editorial review pending. General information, not medical advice.

You are more than your diagnosis

Perspectives from people navigating life with Trisomy 18.

Explore the Trisomy 18 blog
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The Invisible Job: What Caregiving for a Rare Disease Really Looks Like

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Embrace the Ask: How to Seek The Support You Need

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Explore research for Trisomy 18

Explore actively recruiting Trisomy 18 studies with HealthSpark.

HealthSpark

Find actively recruiting studies for Trisomy 18 with HealthSpark. Share your city to explore research near you.

  • Recruiting studies from ClinicalTrials.gov
  • Share your city to look for research near you
  • Eligibility is confirmed by the study team

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Powered by HealthSpark, our AI chat helper · Study information from ClinicalTrials.gov · Eligibility is confirmed by the study team.

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