Patau syndrome, also known as
trisomy 13 and
trisomy D, is a
chromosomalA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
abnormality, a
syndromeIn medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
in which a patient has an additional
chromosome 13Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 114 million base pairs and represents between 3.5 and 4 % of the total DNA in cells....
due to a
nondisjunctionNondisjunction is the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2. This could arise from a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. The result of this error is a...
of chromosomes during
meiosisMeiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
. Some are caused by
Robertsonian translocationRobertsonian translocation is a common form of chromosomal rearrangement that in humans occurs in the five acrocentric chromosome pairs, namely 13, 14, 15, 21, and 22. Other translocations occur but do not lead to a viable fetus. They are named after the American biologist William Rees Brebner...
s. The extra chromosome 13 disrupts the normal course of development, causing heart and kidney defects, amongst other features characteristic of Patau syndrome. Like all
nondisjunctionNondisjunction is the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2. This could arise from a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. The result of this error is a...
conditions (such as
Down syndromeDown syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
and
Edwards syndromeTrisomy 18 is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. It is named after John H. Edwards, who first described the syndrome in 1960...
), the risk of this syndrome in the offspring increases with maternal age at pregnancy, with about 31 years being the average. Patau syndrome affects somewhere between 1 in 10,000 and 1 in 21,700 live births.
Causes
Most cases of Patau's syndrome result from
trisomyA trisomy is a type of polysomy in which there are three copies, instead of the normal two, of a particular chromosome. A trisomy is a type of aneuploidy .-Description and causes:...
13, which means each cell in the body has three copies of chromosome 13 instead of the usual two copies. A small percentage of cases occur when only some of the body's cells have an extra copy, resulting in a mixed population of cells with a differing number of chromosomes; such cases are called mosaic Patau.
Patau syndrome can also occur when part of chromosome 13 becomes attached to another chromosome (translocated) before or at conception. Affected people have two copies of chromosome 13, plus extra material from chromosome 13 attached to another chromosome. With a translocation, the person has a partial trisomy for chromosome 13 and often the physical signs of the syndrome differ from the typical Patau syndrome.
Most cases of Patau syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called non-disjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an
eggAn ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
or
spermA spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
cell may gain an extra copy of the chromosome. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 13 in each of the body's cells. Mosaic Patau syndrome is also not inherited. It occurs as a random error during cell division early in fetal development.
Patau syndrome due to a translocation can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 13 and another chromosome. This rearrangement is called a balanced translocation because there is no extra material from chromosome 13. Although they do not have signs of Patau syndrome, people who carry this type of balanced translocation are at an increased risk of having children with the condition.
Manifestations and physical findings
Of those fetuses that do survive to gestation and subsequent birth, common abnormalites include:
- Nervous system
- Mental
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
and motor challengedMotor skills disorder is a human developmental disorder that impairs motor coordination in daily activities. It is neurological in origin...
- Microcephaly
Microcephaly is a neurodevelopmental disorder in which the circumference of the head is more than two standard deviations smaller than average for the person's age and sex. Microcephaly may be congenital or it may develop in the first few years of life...
- Holoprosencephaly
Holoprosencephaly is a cephalic disorder in which the prosencephalon fails to develop into two hemispheres. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy...
(failure of the forebrain to divide properly).
- Structural eye defects, including microphthalmia
Microphthalmia also referred to as microphthalmos, nanophthalmia or nanophthalmos, is a developmental disorder of the eye that literally means small eye...
, Peters anomaly (a type of eye abnormality), cataractA cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
, iris and/or fundus (colobomaA coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid or optic disc...
), retinal dysplasia or retinal detachmentRetinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
, sensory nystagmus, cortical visual loss, and optic nerve hypoplasiaOptic nerve hypoplasia is a medical condition arising from the underdevelopment of the optic nerve. This condition is the most common congenital optic nerve anomaly. The optic disc appears abnormally small, because not all the optic nerve axons have developed properly...
- Meningomyelocele (a spinal
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
defect)
- Musculoskeletal and cutaneous
- Polydactyly
Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....
(extra digits)
- Low-set ears
Low-set ears is a term used to describe a depressed positioning of the pinna two or more standard deviations below the population average.It can be associated with conditions such as:* Down's syndrome and Turner Syndrome* Noonan syndrome* Patau syndrome...
- Prominent heel
- Deformed feet known as rocker-bottom feet
- Omphalocele
An omphalocele is a type of abdominal wall defect in which the intestines, liver, and occasionally other organs remain outside of the abdomen in a sac because of a defect in the development of the muscles of the abdominal wall.-Presentation:The sac, which is formed from an outpouching of...
(abdominalIn vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
defect)
- Abnormal palm
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
pattern
- Overlapping of fingers over thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
- Cutis aplasia (missing portion of the skin/hair)
- Cleft palate
- Urogenital
- Abnormal genitalia
- Kidney defects
- Other
- Heart defects (ventricular septal defect
A ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...
)
- Single umbilical artery
Occasionally, there is only the one single umbilical artery present in the umbilical cord. Approximately this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality. It is more common in multiple births. Its cause is not known.Most cords have one vein...
Recurrence risk
Unless one of the parents is a carrier of a
translocationIn genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...
the chances of a couple having another trisomy 13 affected child is less than 1% (less than that of
Down SyndromeDown syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
).
History
Trisomy 13 was first observed by
Thomas Bartholin in 1657, but the chromosomal nature of the disease was ascertained by Dr.
Klaus PatauKlaus Patau was a German-born American geneticist. He received his PhD from the University of Berlin in 1936, worked from 1938 to 1939 in London, and then returned to Germany, where he worked at the Kaiser Wilhelm Institute for Biology until 1947. He emigrated to the United States in 1948 and...
in 1960. The disease is named in his honor. Patau syndrome was also described in Pacific island tribes. These reports were thought to have been caused by radiation from atomic bomb tests. The tribes were temporarily moved before and during the test by an
x amount of distance. They were then put back where they had been taken; all of this occurred before it was known how long, or even if, radiation still lingered on after a nuclear explosion.
In England and Wales during 2008–09 there were 172 diagnoses of Patau's syndrome (trisomy 13), with 91% of diagnoses made prenatally. There were 111 elective abortions, 14 stillbirth/miscarriage/fetal deaths, 30 outcomes unknown, and 17 live births. Approximately 4% of Patau's syndrome with unknown outcomes are likely to result in a live birth, therefore the total number of live births is estimated to be 18. The small percentage of babies with the full Patau's syndrome who survive birth and early infancy may live to adulthood, and children with mosaic or partial forms of this trisomy may have a completely different and much more hopeful prognosis.
Treatment
Medical management of children with Trisomy 13 is planned on a case-by-case basis and depends on the individual circumstances of the patient. Treatment of Patau syndrome focuses on the particular physical problems with which each child is born. Many infants have difficulty surviving the first few days or weeks due to severe neurological
problemA problem is an obstacle, impediment, difficulty or challenge, or any situation that invites resolution; the resolution of which is recognized as a solution or contribution toward a known purpose or goal...
s or complex heart defects. Surgery may be necessary to repair heart defects or cleft lip and cleft palate. Physical, occupational, and speech therapy will help individuals with Patau syndrome reach their full developmental potential.
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