What is Patau Syndrome?
Trisomy 13, also known as Patau syndrome, was first identified in 1960 by Dr. Patau and his colleagues as the cause of a specific set of symptoms. These symptoms included brain abnormalities, a lack of observable eyes, cleft palate (a split in the roof of the mouth), hare lip (a split in the upper lip), unusual hand lines, extra thumbs, additional fingers or toes, and birthmarks caused by blood vessels.
Patau syndrome can be identified before birth or at the moment of birth. It’s important to know that the risk of trisomy 13 increases with advanced maternal age, mainly due to a higher chance of what’s called ‘nondisjunction’. Nondisjunction is when chromosomes fail to separate properly. But, it’s worth noting that 20% of Patau syndrome can result from an unequal rearrangement of chromosomes or, very rarely, from a condition called mosaicism, where some cells have a normal number of chromosomes and others do not.
Research has shown that the outlook for patients with Patau syndrome is generally poor. On average, most infants born with this condition live between 7 to 10 days, and 90% do not live beyond their first year. However, there have been some cases of patients living longer due to intensive medical treatment. These long-living patients are less likely to have brain and heart problems, which are usually the main reasons for the poor prognosis associated with Patau syndrome. Even so, those who survive longer are generally expected to have severe disabilities.
What Causes Patau Syndrome?
Patau syndrome is a condition caused by having an extra copy of chromosome 13. This usually happens due to a process called nondisjunction in meiosis. This occurs more often in mothers who are older than 35.
A different cause is a particular genetic event called a Robertsonian translocation. This leads to a person having two normal copies of chromosome 13 and an extra large part of chromosome 13.
A less common cause of Patau syndrome is a condition called mosaicism, where some cells have three copies of chromosome 13, and others have two. Mosaicism is the result of an defect during cell division and isn’t related to a mother’s age.
In terms of prognosis, or likely outcome, those with Patau syndrome due to mosaicism or unbalanced translocations tend to fare better.
Risk Factors and Frequency for Patau Syndrome
Certain genetic irregularities are found in roughly half of all fetal deaths before 20 weeks of pregnancy and in between 6% to 13% of stillbirths. In general, 15% of clinically recognized pregnancies result in fetal death. One particular genetic irregularity, Trisomy 13, is fairly common, affecting 1 in every 5,000 births. This rate is less frequent than Down syndrome, which affects 1 in every 700 births. Edwards syndrome has a similar occurrence rate as Trisomy 13, with about 1 in every 5,000 live births being affected.
Signs and Symptoms of Patau Syndrome
Patau syndrome is a condition that primarily affects newborns and has a myriad of symptoms affecting various parts of the body. These infants usually have poor growth within the womb and small head size. They often have facial defects, abnormal facial features, and issues with the central nervous system. Common facial abnormalities include eyes that are too close together, a divided lip or palate, a sloping forehead, small and formed improperly ears, micrognathia (a condition in which the jaw is undersized), and extra bits of skin in front of the ears. The most common brain abnormality is lobar holoprosencephaly, which occurs when the brain doesn’t divide properly into its right and left halves.
This syndrome also affects the limbs, causing extra digits on the hands or feet, clubfoot, or a condition known as “rocker-bottom feet” that affects the shape of the feet. The syndrome can cause heart defects including holes in the wall separating the heart chambers, tetralogy of Fallot (a combination of four heart defects), and a double outlet right ventricle (two of the main blood vessels leaving the heart arise from the same chamber).
The affected organs might include lungs, liver, kidneys, and parts of the reproductive, digestive, and endocrine systems. More than half of the people with Patau syndrome have other conditions like undescended testicles, malformed penis, underdeveloped labia minora, and a two-horned uterus. Less than half the people with the syndrome have an umbilical hernia, incomplete rotation of the large intestine, Meckel diverticulum (bulge in the small intestine), polycystic kidneys, swollen kidneys due to urine buildup, and a kidney that’s fused at the base.
Patau syndrome survivors often have severe intellectual and motor disabilities, seizures, and they may fail to grow and develop at the expected rate.
Testing for Patau Syndrome
Patau syndrome, also known as trisomy 13, can be diagnosed before a baby is born using several different tests. These tests include something called chorionic villi sampling (a test on tissues from the placenta), amniocentesis (a test on the fluid that surrounds the baby in the womb), or fetal free DNA analysis (a blood test on the mother that searches for baby’s genetic material). These tests are used to detect an extra chromosome 13 in the baby’s cells.
An ultrasound scan, typically done after the 17th week of pregnancy, can also aid in detecting Patau syndrome. This is because the syndrome often results in certain physical deformities like brain abnormalities, unusual facial features, skeletal problems, and heart or kidney defects, which can potentially be seen during the ultrasound. However, any abnormal findings from the ultrasound should be further confirmed with a genetic test on fetal cells.
A method called tissue microarray has improved our ability to diagnose genetic changes in cases of stillbirth, especially when the baby’s body is decomposed. This technique helps to identify genetic changes by studying small sections of tissue.
Treatment Options for Patau Syndrome
Treating Patau syndrome, a genetic disorder with a generally poor outlook, is often a topic of debate, as it’s uncertain whether intensive treatment can significantly improve the patients’ prognosis.
At birth, babies diagnosed with Patau syndrome may need additional oxygen and help with breathing, which might involve a procedure to open the airway (intubation) or creating an opening in the neck to the windpipe (tracheostomy) due to facial abnormalities. If the baby has heart defects, they might need heart surgery to fix them. There could also be a need for other surgeries to fix common issues such as hernias, cleft lip, difficulties with feeding, or problems with bones and joints.
Furthermore, the newborn might need special nutritional care, concurrent medications to prevent seizures, prophylactic antibiotics to guard against urinary tract infections, and possibly the use of hearing aids.
Even with the most aggressive management, the average life span for patients with Patau syndrome tends to be about two years.
What else can Patau Syndrome be?
Patau syndrome, also known as trisomy 13 in a fetus, might show similar ultrasound signs to other conditions like Edwards syndrome (trisomy 18), Down syndrome (trisomy 21) or different chromosomal disorders. To accurately separate trisomy 13 from these other abnormalities, certain tests are used. These include:
- Chorionic villi sampling
- Amniocentesis
- Fetal free DNA analysis
- Tissue microarray
What to expect with Patau Syndrome
Large-scale research studies have shown that people with Patau syndrome generally have a poor prognosis. Patau syndrome is a genetic disorder that has serious effects on the body’s development. Historically, the those who are live-born with this syndrome usually survive for a median of 7 to 10 days, and 90% do not live past their first year.
However, recent case studies have shown that aggressive medical treatment can lead to greater survival durations. Patau syndrome has different forms and those with the mosaic type or the unbalanced translocations type generally have a better prognosis. “Mosaic” refers to having a mixture of cells with the normal number of chromosomes and cells with an extra chromosome 13 and “unbalanced translocations” are when a child is born with both an extra and missing chromosome.
Aggressive medical management, which often involves both surgical intervention and medicine, may help to extend median survival to approximately 733 days (about 2 years) according to a recent study.
Possible Complications When Diagnosed with Patau Syndrome
Most individuals with Patau syndrome, about 90%, unfortunately, do not live past their first year after birth, and many do not survive even until birth. If a patient with Patau syndrome does manage to survive past their infant years, they often face many complications due to typical birth defects associated with the condition.
Preventing Patau Syndrome
Health conditions caused by extra chromosomes, known as trisomies, and other genetic abnormalities are more frequently seen in pregnancies of older women. If you’re a woman considering getting pregnant in your later years, you should be aware of this increased risk. Specifically, if a baby is diagnosed with Patau syndrome – a condition caused by an extra copy of chromosome 13 – the family should know that this disorder often leads to severe health problems.
