Also called trisomy 13, it is a congenital disorder (present at birth) associated with the presence of an extra copy of chromosome 13.
The extra chromosome 13 causes numerous physical and mental abnormalities, especially heart defects .
Patau syndrome is named for Klaus Patau, who reported the syndrome and its association with trisomy in 1960.
Patau syndrome causes serious physical and mental abnormalities, including heart defects, incomplete brain development, and unusual facial features.
Due to the severity of these conditions, less than 20 percent of those affected by Patau syndrome survive beyond childhood.
Causes of Patau syndrome
Children normally inherit 23 chromosomes from each parent, for a total of 46 chromosomes.
A typical human has 46 chromosomes, 22 pairs of non-sex chromosomes, and a pair of sex-linked chromosomes that determine the sex of the individual.
Sometimes a child can end up with more than 46 chromosomes due to problems with the father’s sperm or the mother’s egg or due to mutations that occurred after the sperm and egg fused to form the embryo, at conception.
A condition called trisomy occurs when three, rather than two copies of a chromosome are present in a developing human embryo.
An extra copy of a particular chromosome can come from the egg or sperm or from mutations that occur after conception.
The best-known disorder related to trisomy is Down syndrome (trisomy 21), in which the developing embryo has an extra copy of chromosome 21.
In this disorder, the developing embryo has three copies of chromosome 13. An extra copy of chromosome 13 is not the only cause of Patau syndrome.
Other changes on chromosome 13, such as incorrect placement (translocation), can also lead to features classified as Patau syndrome.
In these cases, an error occurs that causes a part of chromosome 13 to be swapped for a portion of another chromosome.
There is no production of additional chromosomes, but a part of each affected chromosome is “out of place” or translocated to another chromosome.
The severity and symptoms of Patau syndrome vary with the type of chromosomal abnormality, from extremely serious conditions to almost normal appearance and function.
Total trisomy 13, which is present in most cases, produces the most serious and numerous internal and external abnormalities such as:
In the brain
Commonly, the forebrain is not divided into lobes or hemispheres (holoprosencephaly), and the entire head is unusually small (microcephaly).
The spinal cord may protrude through a cystic mass in the vertebrae of the spine (myelomeningocele).
Children who survive infancy are profoundly mentally retarded and may experience seizures.
Eyes and ears
Incomplete development of the optic and olfactory nerves often accompanies the brain defects described above.
The eyes may be unusually small (microphthalmia) or one eye may be absent (anophthalmia).
The eyes are sometimes placed close together (hypotelorism) or even merge into a single structure.
The incomplete development of any structure in the eye (coloboma) or the failure of the retina to develop properly (retinal dysplasia) leads to vision problems.
People affected by Patau syndrome can be born partially or totally deaf, and many are subject to recurrent ear infections.
The facial features of many people affected by Patau syndrome appear squashed. The ears are generally malformed and rotated.
Often a child with trisomy 13 has a cleft lip, cleft palate, or both.
Other physical features include loose skin folds at the back of the neck, extra toes (polydactyly), permanently flexed toes (camptodactyly), markedly prominent heels, “rocker foot,” and missing ribs.
Genital malformations are common in people affected by Patau syndrome and include undescended testes (cryptorchidism), abnormally developed scrotum and ambiguous genitalia in men, or an abnormally shaped uterus (bicornuate uterus) in women.
Respiratory, kidney, gastrointestinal and heart problems
In almost all cases, children affected by Patau syndrome have breathing difficulties and heart defects, including defects of the atrial and ventricular septum (holes between the chambers of the heart).
Also malformed ducts that cause an abnormal direction of blood flow (patent ductus arteriosus), holes in the valves of the lungs and heart (pulmonary and aortic valves).
They can also present an abnormal position of the heart, this is located on the right side, instead of the left side of the chest (dextrocardia).
The kidneys and gastrointestinal system can also be affected by cysts similar to those seen in polycystic kidney disease.
These defects are often severe and life-threatening.
Partial trisomy of the distal segment of chromosome 13 produces generally less severe but still severe symptoms and a distinctive facial appearance that includes a short, upturned nose.
A longer-than-usual area between the nose and upper lip (philtrum), thick eyebrows, and tumors formed by blood capillaries on the forehead (frontal capillary hemangioma).
Partial trisomy of the proximal segment of chromosome 13 is much less likely to be fatal and has been associated with a variety of facial features, including a large nose, a short upper lip, and a receding jaw.
Both forms of partial trisomy also result in severe mental retardation.
When the baby is more than a month old, other symptoms appear that are observed in people with Patau syndrome, these are:
- Feeding difficulties and constipation.
- Reflux disease
- Slow growth rates.
- Curvature of the spine (scoliosis).
- Sensitivity to sunlight.
- Low muscle tone.
- High blood pressure
- Sinus infections.
- Urinary tract infections and ear and eye infections.
Patau syndrome diagnosis
Patau syndrome is detectable during pregnancy through the use of ultrasound imaging (sonography).
A combined screening test or a mother’s serum screening test may show some abnormalities.
You can also opt for a non-invasive prenatal test to learn about the risk of having a baby with Patau syndrome.
About 90 percent of babies affected by Patau syndrome are detected on examination.
More tests such as amniocentesis or chorionic villus sampling are needed to confirm the diagnosis.
At birth, the numerous malformations of the newborn indicate a possible chromosomal abnormality.
Trisomy 13 is confirmed by examining the baby’s chromosome pattern through karyotype or another procedure.
Karyotype involves the separation and isolation of chromosomes present in cells taken from an individual.
These cells are usually taken from cells found in a blood sample.
The 22 non-sex chromosomes are identified by size, from largest to smallest, such as chromosomes 1 through 22. Chromosomes that determine sex are also identified.
Patau syndrome is confirmed by the presence of three, rather than the normal two copies of the thirteenth largest chromosome.
Babies with Edward Syndrome and Patau Syndrome can have similar characteristics and make it difficult for doctors to differentiate.
Naturally, the differential diagnosis should aim to properly distinguish between the symptoms of these two conditions and confirm the presence of Patau syndrome.
A mild pregnancy ultrasound can reveal certain abnormalities. However, further tests such as chorionic villus sampling or amniocentesis are required to confirm the presence of the disorder.
Some babies born with Patau syndrome have serious and incurable birth defects. However, children with better prognoses require medical treatment to correct structural abnormalities and associated complications.
For feeding problems, special formulas, positions and techniques can be used. Tube feeding or placement of a gastric tube may even require gastrostomy.
Structural abnormalities such as cleft lip and palate can be corrected by surgery. Special diets, hearing aids, and visual aids can be used to mitigate some symptoms of Patau syndrome.
Physical therapy, speech therapy, and other types of developmental therapy help a child reach his full developmental potential. Treating children with this disorder involves individual planning.
The forms of healing administered to a patient are based on their particular condition.
Treatment for this disorder is usually aimed at treating the specific physical symptoms that the affected child is born with.
Many babies have a hard time surviving in the first days or weeks after birth due to complex heart defects or acute neurological problems.
In some cases, surgery may be necessary to repair heart defects.
Surgical intervention is generally delayed for the first few months after birth due to the high mortality rate associated with the disease.
Since the translocation form of Patau syndrome is genetically transmitted, genetic counseling for parents should be part of the treatment of the disease.
Patau syndrome complications
Complications due to this disorder begin almost immediately after birth.
Possible complications associated with this condition include:
- Heart failure .
- Eye sight problems.
- Feeding problems
- Trouble breathing
About 45 percent of babies with trisomy 13 die within their first month of life; up to 70 percent in the first six months; and more than 70 percent for one year of age.
Survival to adulthood is very rare. Only one adult is known to have survived to age 33.
Most of the survivors have profound mental and physical disabilities; however, the learning capacity in children with Patau syndrome varies from case to case.
Older children can walk with or without a walker.
They may also be able to understand words and phrases, follow simple commands, use some words or signs, and recognize and interact with others.
Patau syndrome prevention
There is no known way to prevent Patau syndrome, although it can be diagnosed prenatally by amniocentesis.
Parents of children born with Patau syndrome should prepare for the possibility of their child dying within days or weeks of birth, in addition to past survival rates after early childhood.
Likewise, parents who already had a child with Patau’s disease and want to have another child should discuss possible problems with the specialist doctor.