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Living with Monosomy 13q34

A rare chromosome condition with developmental delay, mild intellectual disability, weight gain, and mild facial differences.

Understanding Monosomy 13q34

Monosomy 13q34 is a rare chromosome condition caused by a missing piece of the long arm of chromosome 13.

It is mainly marked by global developmental delay, mild intellectual disability, obesity, and mild differences in facial features. Other features vary and can include heart defects present from birth, extra fingers or toes, and a missing corpus callosum (the bridge between the two sides of the brain). Signs are seen during pregnancy or in the newborn period.

Signs & symptoms

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

  • Delays in reaching developmental milestones
  • Mild intellectual disability
  • Obesity
  • Smaller-than-average head size (microcephaly)
  • Broad forehead and prominent nose
  • Eyes set widely apart

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 eye disease specialists and genetic specialists.

  3. Ask which tests can help

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

Care & treatment

Care team
Eye disease specialists (ophthalmologists); Genetic specialists (geneticists)
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 Disorder Outreach
  • 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
Can chromosome testing confirm which part of chromosome 13 is missing?
Should heart and brain scans be done?
What developmental and weight support is available?

Quick facts

Symptoms usually startduring Pregnancy and as a Newborn

This condition results from a partial deletion of the long arm of chromosome 13. GARD says changes in genes (also called variants) cause it.

Genetic

Also known as: del(13)(q34); distal deletion 13q34; monosomy 13q34 syndrome; monosomy type 13q34; subtelomeric deletion 13q34

Patient organizations

Broader rare-disease groups

Source: NIH GARD · Monosomy 13q34GARD ID 16847 · 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 Monosomy 13q34.

Explore the Monosomy 13q34 blog

Explore research for Monosomy 13q34

Explore actively recruiting Monosomy 13q34 studies with HealthSpark.

HealthSpark

Find actively recruiting studies for Monosomy 13q34 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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