Trisomy 13: MedlinePlus Medical Encyclopedia

P Trisomy 13 (also called Patau syndrome) is a genetic disorder in which a person has 3 copies of genetic material from chromosome 13, instead of the usual 2 copies. Rarely, the extra material may be attached to another chromosome (translocation).

T Causes
P 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.
- Trisomy 13: mosaicism, the presence of an extra chromosome 13 in some of the cells.
- Partial trisomy: the presence of a part of an extra chromosome 13 in the cells.
P The extra material interferes with normal development.
P 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.

T Symptoms
P 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 1
- 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)

T Exams and Tests
P 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
P Gastrointestinal x-rays or ultrasound may show rotation of the internal organs.
P 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.
P Chromosome studies show trisomy 13, trisomy 13 mosaicism, or partial trisomy.

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

T Support Groups
P Support groups for trisomy 13 include:
- Support Organization for Trisomy 18, 13 and Related Disorders (SOFT): trisomy.org
- Hope for Trisomy 13 and 18: www.hopefortrisomy13and18.org

T Outlook (Prognosis)
P More than 90% of children with trisomy 13 die in the first year.

T Possible Complications
P Complications begin almost immediately. Most infants with trisomy 13 have congenital heart disease.
P Complications may include:
- Breathing difficulty or lack of breathing (apnea)
- Deafness
- Feeding problems
- Heart failure
- Seizures
- Vision problems

T When to Contact a Medical Professional
P Call 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.

T Prevention
P Trisomy 13 can be diagnosed before birth by amniocentesis with chromosome studies of the amniotic cells.
P Parents of infants with trisomy 13 that is caused by a translocation should have genetic testing and counseling. This may help them avoid having another child with the condition.

T Alternative Names
P Patau syndrome

T Images
- Polydactyly - an infant's hand
- Syndactyly

T References
P Bacino CA, Lee B. Cytogenetics. In: Kliegman RM, Stanton BF, St. Geme JW III, Shor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 81.

T Review Date 8/1/2015
P Updated by: Chad Haldeman-Englert, MD, FACMG, Fullerton Genetics Center, Asheville, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

