Trisomy 13 occurs when extra DNA from chromosome 13 appears in some or all of the body's cells.

• Trisomy 13: the presence of an extra (third) chromosome 13 in all of the cells.
• Mosaic trisomy 13: the presence of an extra chromosome 13 in some of the cells.
• Partial trisomy 13: the presence of a part of an extra chromosome 13 in the cells.

The extra material interferes with normal development.

Trisomy 13 occurs in about 1 out of every 10,000 newborns. Most cases are not passed down through families (inherited). Instead, the events that lead to trisomy 13 occur in either the sperm or the egg that forms the fetus.

Symptoms include:

• Cleft lip or palate
• Clenched hands (with outer fingers on top of the inner fingers)
• Close-set eyes -- eyes may actually fuse together into one
• Decreased muscle tone
• Extra fingers or toes (polydactyly)
• Hernias: umbilical hernia, inguinal hernia
• Hole, split, or cleft in the iris (coloboma)
• Low-set ears
• Intellectual disability, severe
• Scalp defects (missing skin)
• Seizures
• Single palmar crease
• Skeletal (limb) abnormalities
• Small eyes
• Small head (microcephaly)
• Small lower jaw (micrognathia)
• Undescended testicle (cryptorchidism)

The infant may have a single umbilical artery at birth. There are often signs of congenital heart disease, such as:

• Abnormal placement of the heart toward the right side of the chest instead of the left
• Atrial septal defect
• Patent ductus arteriosus
• Ventricular septal defect

Gastrointestinal x-rays or ultrasound may show rotation of the internal organs.

MRI or CT scans of the head may reveal a problem with the structure of the brain. The problem is called holoprosencephaly. It is the joining together of the 2 sides of the brain.

Chromosome studies show trisomy 13, trisomy 13 mosaicism, or partial trisomy. Rarely, the extra material may be attached to another chromosome (translocation).

There is no specific treatment for trisomy 13. Treatment varies from child to child and depends on the specific symptoms.

More information and support for people with Trisomy 13 condition and their families can be found at:

• Support Organization for Trisomy 18, 13 and Related Disorders (SOFT): trisomy.org
• Hope for Trisomy 13 and 18: www.hopefortrisomy13and18.org

More than 90% of children with trisomy 13 die in the first year.

Complications begin almost immediately. Most infants with trisomy 13 have congenital heart disease.

Complications may include:

• Breathing difficulty or lack of breathing (apnea)
• Deafness
• Feeding problems
• Heart failure
• Seizures
• Vision problems

Contact your health care provider if you have had a child with trisomy 13 and you plan to have another child. Genetic counseling can help families understand the condition, the risk of inheriting it, and how to care for the person.

Trisomy 13 can be diagnosed before birth by amniocentesis with chromosome studies of the amniotic cells.

Parents of infants with trisomy 13 that is caused by a translocation should have genetic testing and counseling. This may help them be aware of the chances of having another child with the condition.

Patau syndrome

Bacino CA, Lee B. Cytogenetics. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 98.

Madan-Khetarpal S, Arnold G, Ortiz D. Genetic disorders and dysmorphic conditions. In: Zitelli BJ, McIntire SC, Nowalk AJ, Garrison J, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 1.

National Center for Advancing Translational Sciences. Genetic and Rare Diseases Information Center website. Trisomy 13. rarediseases.info.nih.gov/diseases/7341/trisomy-13. Updated February 2023. Accessed October 17, 2023.

Updated by: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.