Is Trisomy 13 Syndrome / Patau Syndrome hereditary?

Trisomy 13 Syndrome, also known as Patau syndrome, is a genetic condition but is rarely hereditary. In the vast majority of cases, it occurs as a de novo (spontaneous) event during the formation of reproductive cells, meaning it is not passed down from parents to their children.

Is Trisomy 13 Syndrome hereditary?

While Trisomy 13 Syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 13, it is typically not inherited. The condition is usually caused by nondisjunction, a random error in cell division during the development of an egg or sperm. Because this is a sporadic event, the recurrence risk for parents who have had one child with Trisomy 13 Syndrome is generally very low, typically estimated at less than 1%.

What are the different types of Patau syndrome?

There are three primary ways the genetic error manifests in Trisomy 13 Syndrome:

• Full Trisomy 13: The most common form, where every cell in the body contains an extra chromosome 13. This is almost always a spontaneous event.


• Translocation Trisomy 13: A rare form where an extra part of chromosome 13 attaches to another chromosome. This is the only type that can occasionally be inherited from a parent who carries a "balanced translocation."


• Mosaic Trisomy 13: Occurs when only some of the body's cells contain the extra chromosome, typically resulting from an error after fertilization.

How is genetic testing used for diagnosis?

Genetic testing is essential for confirming a diagnosis of Trisomy 13 Syndrome. Prenatal diagnosis can be performed via chorionic villus sampling (CVS) or amniocentesis. After birth, a chromosomal analysis (karyotype) is used to confirm the diagnosis and determine if it is a full trisomy or a translocation, which helps clinical geneticists determine if parental testing is necessary to assess future recurrence risks.

The role of genetic counseling

Genetic counseling is strongly recommended for families affected by Trisomy 13 Syndrome. A counselor can help explain the specific chromosomal results, provide emotional support for the family, and clarify the low risk of recurrence. If a translocation is identified, the counselor will offer testing for both parents to see if one carries a balanced rearrangement, which has implications for future family planning.

Next steps

• Consult with a board-certified clinical geneticist to review chromosomal findings.


• Connect with the 31 members of the DiseaseMaps community who have experience with Trisomy 13 Syndrome.


• Discuss prenatal screening options with an OB-GYN or maternal-fetal medicine specialist if planning future pregnancies.

Medical disclaimer: This information is for educational purposes only 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


• Support Organization for Trisomy 18, 13, and Related Disorders (SOFT)