Short answer · Medically reviewed summary · Last updated: 2026-05-08
Trisomy 13 Syndrome, also known as Patau syndrome, is caused by the presence of an extra copy of chromosome 13 in the body's cells, which disrupts normal fetal development. This chromosomal abnormality typically occurs as a random event during the formation of reproductive cells or early embryonic development rather than being inherited from parents. What causes Trisomy 13 Syndrome at a genetic level? The primary cause of Trisomy 13 Syndrome is nondisjunction, a failure of chromosome 13 pairs to separate properly during meiosis.
Which are the causes of Trisomy 13 Syndrome / Patau Syndrome?
Causes of Trisomy 13 Syndrome / Patau Syndrome explained: genetic and environmental factors, reviewed against medical sources, plus patient perspectives.
Trisomy 13 Syndrome, also known as Patau syndrome, is caused by the presence of an extra copy of chromosome 13 in the body's cells, which disrupts normal fetal development. This chromosomal abnormality typically occurs as a random event during the formation of reproductive cells or early embryonic development rather than being inherited from parents.
What causes Trisomy 13 Syndrome at a genetic level?
The primary cause of Trisomy 13 Syndrome is nondisjunction, a failure of chromosome 13 pairs to separate properly during meiosis. This results in an egg or sperm cell carrying an extra chromosome 13. When fertilization occurs, the embryo ends up with three copies of chromosome 13 instead of the usual two. There are three primary genetic mechanisms for this:
- Full Trisomy 13: Every cell in the body contains an extra chromosome 13 (approx. 75-80% of cases).
- Translocation Trisomy 13: An extra part of chromosome 13 attaches to another chromosome; this is the only form that can occasionally be inherited from a parent who carries a "balanced" translocation.
- Mosaic Trisomy 13: Only some of the body's cells have an extra chromosome 13, which can sometimes lead to a milder clinical presentation.
Are there environmental risk factors for Patau syndrome?
Currently, there is no evidence linking Trisomy 13 Syndrome to environmental triggers, lifestyle choices, or maternal behavior. The only statistically significant risk factor identified for the most common form of Trisomy 13 Syndrome is advanced maternal age, which increases the likelihood of errors during egg cell division. It is important to clarify that this is a biological risk factor, not a cause, and the condition remains a random occurrence for the vast majority of families.
What is the status of research into the etiology of Trisomy 13 Syndrome?
While the chromosomal basis of Trisomy 13 Syndrome is well-understood, researchers are currently investigating the specific gene expression patterns that lead to the severe physical and developmental challenges associated with the syndrome. Our DiseaseMaps.org community of 31 members continues to highlight the need for further research into how these extra genes affect organ system development, which remains a focus of modern pediatric genetics.
Next steps
- Consult with a clinical geneticist to discuss recurrence risks and chromosomal analysis.
- Connect with the 31 other families on DiseaseMaps.org to share experiences and find support.
- Review resources from the NIH GARD for updated clinical trial information.
Medical disclaimer: This information is for educational purposes and should not replace professional medical advice, diagnosis, or treatment.
References
- NIH Genetic and Rare Diseases Information Center (GARD): Trisomy 13
- Orphanet: Patau syndrome
- OMIM (Online Mendelian Inheritance in Man): Trisomy 13
- SOFT (Support Organization for Trisomy 18, 13, and Related Disorders)
