Trisomy 13 Patau Syndrome

Patau syndrome is  a rare genetic disorder that occurs when a child is born with three copies of chromosome 13 in every cell (trisomy 13). Trisomy 13 occurs in about 1 out every 10,000 newborns. Most babies with this abnormality do not survive to term; infants that do survive usually die within a year. This incredibly debilitating chromosomal abnormality is usually caused by an error in meiosis, or sex-cell division. This syndrome can lead to severe difficulties in meeting the challenges of life.

How It Can Happen

Patau Syndrome is a genetic disorder that results from abnormal meiosis that affects chromosome 13.

In normal meiosis, a human egg or sperm cell is produced with 23 chromosomes. This egg or sperm then joins another egg or sperm, producing a fertilized cell with 46 chromosomes, 23 chromosomes from each parent. In abnormal meiosis, an egg, or very rarely a sperm cell, will be produced with an extra 13th chromosome. This may happen during meiosis I when chromosomes segregate.

As the chromosomes separate in cell division, something goes awry during chromosomal segregation. In abnormal cell division, instead of one chromosome being distributed to each cell, both chromosomes get funneled into one cell, with the other cell missing that chromosome. This results in an egg with an extra thirteenth chromosome. When this egg is fertilized with a normal sperm, it produces a fertilized zygote with 47 chromosomes, revealing trisomy 13. Most of these fetuses are aborted in miscarriage. The babies that do survive to term experience severe difficulties. Visit website to see a karyotype, or genetic map, demonstrating trisomy 13.

Symptoms and Complications

Trisomy 13, or Patau syndrome, has a myriad of debilitating physical symptoms. These physical symptoms often include a cleft lip and/or a cleft palate. Thus, the infant has severe difficulty latching onto a nipple to feed and may suffer from mild to severe malnutrition.

Babies often experience severe complications in vision. Some babies are born with a hole, split, or cleft in the iris of the eye (coloboma), close-set eyes or even one fused eye (cyclopia). The infant may also have low-set ears, an abnormally small head (microcephaly), and/or missing skin on the scalp or scalp defects. Male infants may be born with an undescended testicle. Some babies are born with an umbilical and/or inguinal hernia.

Children who exhibit Patau syndrome often show signs of severe congenital heart failure. These signs may include a persistent ductus arteriosus, the fetal passageway between the superior vena cava and the aorta which usually disappears in full-term children, or an atrial or ventricular septal defect (literally a hole in heart).

Often signs of the extra chromosome appear on the infant’s extremities. The infant will most likely have extra fingers or extra toes (polydactyly).

Mental symptoms include severe mental retardation and seizures.  Other complications include difficulty breathing or lack of breathing (respiratory apnea), deafness, severe feeding problems, heart failure, seizures, and vision problems.

Is there a cure?

There is no cure for a genetic abnormality. Treatment includes making the baby as comfortable as possible. Parents and family members of children with Patau syndrome may want to consider support and/or professional counseling. They can seek support here.