What is Trisomy 13?
Also known as Patau Syndrome, Trisomy 13 is a genetic disorder in which the person gets three copies of chromosome 13, which in normal cases, is two copies. This extra copy of chromosome may cause neurological and heart defects making it challenging for infants to survive.
Based on extra DNA from chromosome 13 present in some or all body cells, Trisomy 13 can be further classified into following types:
i. Trisomy 13- When DNA from chromosome 13 is present in all body’s cells.
ii. Trisomy 13 mosaicism- When DNA from chromosome 13 is present in some of the cells.
iii. Partial trisomy – When only a part of third chromosome is present in the body cells.
The occurrence of this syndrome is least common among the three autosomal trisomies: Trisomy 21, Trisomy 18 and Trisomy 13. Patau Syndrome usually affect females more than males because of the fact that male fetus having this syndrome could not survive till birth.
Trisomy 13 is found in every 1 of 10,000 babies born. Trisomy 13 is associated with the age of the mother and can affect people of any background. Generally Patau syndrome is not passed down through heredity but the syndrome occurs due to abnormalities in sperm or egg during fetus formation.
Trisomy 13 life expectancy
More than 80% of the children born with Trisomy 13 die within the first year. Sad but true, prognosis for child born with Trisomy 13 is very less but such babies are still born. Some babies with Trisomy 13 will survive the pregnancy and some of the babies survive only their first month of birth. However it becomes difficult to predict the life expectancy of a child born with Trisomy 13 if no life threatening problems exist at the time of birth. In rarest of the rare case, the child may survive teenage as well.
In a normal case, sperm and egg unite at the time of fertilization to form 23 chromosome pairs or 46 chromosomes. However abnormality occurs when sperm and egg are forming and an extra chromosome i.e. chromosome 13 is released to the embryo. This extra chromosome can come either from father’s sperm cell or mother’s egg cell.
Sometimes chromosome 13 is already attached to another chromosome in the sperm or egg. This condition is also known as translocation. If this occurs, trisomy 13 is inherited in the family.
Trisomy 13 Symptoms
The symptoms of characteristics of Trisomy 13 include:
• Polydactyl i.e. extra toe or finger may be present
• Clenched hands
• Small eyes or eyes may fuse into one another to form close-set eyes
• Reduced muscle tone
• Umbilical and Inguinal hernia
• Split, cleft or hole present in the iris.
• Scalp defects including missing skin on the scalp
• Micrognathia- small lower jaw
• Cryptorchidism – undescended testicle
• Seizures and limb abnormalities
• Rocker bottom (deformed) feet
• Heart and kidney defects
• Neurological defects- microcephaly i.e. small head, holoprosencephaly i.e. brain doesn’t divide into two during gestation period and mental problems.
• Other facial defects- Microphthalmia i.e. small eyes, deformed nose and cleft palate or lip.
The symptoms of Trisomy 13 are evident at the time of birth. It has been reported that sometimes Trisomy 13 is mistaken with Trisomy 18 which can be prevented by conducting genetic testing. Usually computed tomography and magnetic resonance imaging are done to detect the condition of heart, brain and kidney. Echocardiogram which is an ultrasound of heart can be done to know more about associated heart defects.
Gastrointestinal X-ray and ultrasounds can be done to detect the rotation of internal organs. Chromosome studies can be conducted to know whether it’s partial, full or mosaicism.
Trisomy 13 treatment
Treatment of Trisomy 13 depends on individual developing the kind of abnormality from this syndrome. It is seen that in most of the cases infants have problem in surviving the first few weeks owing to severe heart and neurological problems. For facial deformations like cleft lip or cleft palate and for heart defects, surgery is required.
Also, physical and speech therapy help the patients in attaining full developmental potential to a great extent.
Prognosis and complications
Trisomy 13 is associated with a number of complications which begin immediately. Some of the complications include:
• Congenital heart disease
• Problem in feeding
• Difficulty in breathing or breathlessness
• Vision problems
• Heart failure
If you see any symptoms of Trisomy 13 in your child, see your health care provider immediately. Also if you already have one child with Trisomy 13 and you are planning for the next child, you should see the doctor first. Genetic counseling can help a great way in understanding the condition and ways to prevent risk of inheriting it further.
The syndrome is a genetic disorder and is difficult to prevent. But it can be diagnosed before birth by amniocentesis. Parents with Trisomy 13 should get genetic testing and counseling done to know the likelihood of their baby developing this condition.