Triploid syndrome, also called triploidy, is a chromosomal disorder in which a fetus has three copies of every

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

instead of the normal two. If this occurs in only some cells, it is called

mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...

triploidy and is less severe. Most embryos with triploidy miscarry early in development.

Signs and symptoms

Many organ systems are affected by triploidy, but the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

and skeleton are the most severely affected: Common central nervous system defects seen in triploidy include

holoprosencephaly Holoprosencephaly (HPE) is a cephalic disorder in which the prosencephalon (the forebrain of the embryo) fails to Prenatal development, develop into two Cerebral hemisphere, hemispheres, typically occurring between the 18th and 28th day of gestati ...

hydrocephalus Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain, which can cause pressure to increase in the skull. Symptoms may vary according to age. Headaches and double vision are common. Elderly adults with n ...

(increased amount of cerebrospinal fluid within the brain),

ventriculomegaly Ventriculomegaly is a brain condition that mainly occurs in the fetus when the lateral ventricles become dilated. The most common definition uses a width of the atrium of the lateral ventricle of greater than 10 mm. This occurs in around 1 ...

, Arnold–Chiari malformation, agenesis of the corpus callosum and neural tube defects. Skeletal manifestations include cleft lip/palate,

hypertelorism Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits (eyes), or orbital hypertelorism. In this condition, the distance between the inner eye corners, a ...

club foot Clubfoot is a congenital or acquired defect where one or both feet are supinated, rotated inward and plantar flexion, downward. Congenital clubfoot is the most common congenital malformation of the foot with an incidence of 1 per 1000 births. ...

and syndactyly of fingers three and four.

Congenital heart defect A congenital heart defect (CHD), also known as a congenital heart anomaly, congenital cardiovascular malformation, and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital h ...

hydronephrosis Hydronephrosis is the hydrostatic dilation of the renal pelvis and Renal calyx, calyces as a result of obstruction to urine flow downstream. Alternatively, hydroureter describes the dilation of the ureter, and hydronephroureter describes the dila ...

omphalocele An omphalocele or omphalocoele, also known as an exomphalos, is a rare abdominal wall defect. Beginning at the 6th week of development, rapid elongation of the gut and increased liver size reduces intra abdominal space, which pushes intestinal lo ...

and meningocele (

spina bifida Spina bifida (SB; ; Latin for 'split spine') is a birth defect in which there is incomplete closing of the vertebral column, spine and the meninges, membranes around the spinal cord during embryonic development, early development in pregnancy. T ...

) are also common.

Cystic hygroma A cystic hygroma is a form of lymphatic malformation. It is an abnormal growth that usually appears on a baby's neck or head. It consists of one or more cysts and tends to grow larger over time. The disorder usually develops while the fetus is s ...

s occur but are uncommon. Triploid fetuses have intrauterine growth restriction beginning early in the pregnancy, as early as 12 weeks, and does not affect the head as severely as the body.

Oligohydramnios Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. The limiting case is anhydramnios, where there is a complete absence of ...

, low levels of amniotic fluid, is common in triploid pregnancies. Placental abnormalities are common in triploidy. Most frequently, the placenta is enlarged and may have cysts within. In some cases, the placenta may be unusually small, having ceased to grow. During the first trimester, fetuses with triploidy have a thicker fluid under the skin behind their neck, which calls for observation during the first and second trimester of gestation. The mother will usually have high levels of specific proteins including maternal serum alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (hCG). Symptoms may include, but are not limited to, swelling,

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

, or

hypertension Hypertension, also known as high blood pressure, is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not cause symptoms i ...

. Infants may show facial abnormalities, micrognathia,

cleft lip A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate occurs when the palate (the roof of the mouth) contains an opening into the nasal cavi ...

, as well as other birth defects that result from kidney, limb, and umbilical cord complications. They are also prone to being smaller than a normal sized newborn, a problem that arises while the infant is still a fetus.

Causes

Triploidy is caused by an extra set of chromosomes. Triploidy can result from either two

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

fertilizing one

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

(

polyspermy In biology, polyspermy describes the Fertilisation, fertilization of an Ovum, egg by more than one Spermatozoon, sperm. Ploidy, Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspe ...

) (60%) or from one sperm fertilizing an egg with two copies of every chromosome (40%). These are otherwise known as diandric fertilization and digynic fertilization. Pregnancies caused by digynic fertilization are more likely to end right before a baby is due for full term. Pregnancies caused by diandric fertilization result in a miscarriage towards the first trimester. Another factor known as a partial mole pregnancy can cause triploidy. It is known to cause early termination, cancer, and even a second molar pregnancy.

Diagnosis

Triploidy may be suggested by dramatically elevated levels of serum alpha-fetoprotein. On

obstetric ultrasonography Obstetric ultrasonography, or prenatal ultrasound, is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in the uterus (womb). The procedure is a stand ...

, abnormalities of the skeleton, central nervous system, heart, abdomen, and kidneys are visible in the most severe cases beginning at 12-14 weeks of pregnancy. Placental abnormalities associated with a triploid pregnancy become visible at 12-14 weeks. Placentomegaly or intrauterine growth restriction are the typical findings that prompt evaluation for triploidy, though oligohydramnios may be the first sign in some cases. Placentomegaly is not pathognomonic for triploidy because in some cases, the placenta senesces. Triploidy must be distinguished from trisomy 13 and trisomy 18, which may appear similar on sonography.

Genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...

allows for a definitive diagnosis. A sample of amniotic fluid can also be tested to diagnose triploidy.

Prognosis

Most fetuses with triploidy do not survive to birth, and those that do usually die within days. As there is no treatment for triploidy,

palliative care Palliative care (from Latin root "to cloak") is an interdisciplinary medical care-giving approach aimed at optimizing quality of life and mitigating or reducing suffering among people with serious, complex, and often terminal illnesses. Man ...

is given if a baby survives to birth. If triploidy is diagnosed during the pregnancy, termination is often offered as an option due to the additional health risks for the mother (

pre-eclampsia Pre-eclampsia is a multi-system disorder specific to pregnancy, characterized by the new onset of hypertension, high blood pressure and often a significant amount of proteinuria, protein in the urine or by the new onset of high blood pressure a ...

, a life-threatening condition, or choriocarcinoma, a type of cancer). Should a mother decide to carry until term or until a spontaneous miscarriage occurs, doctors will monitor her closely in case either condition develops.

Mosaic A mosaic () is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/Mortar (masonry), mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and ...

triploidy has an improved prognosis, but affected individuals have moderate to severe

cognitive disabilities There are a variety of disabilities affecting cognitive ability. This is a broad concept encompassing various Intellectual disability, intellectual or cognitive deficits, including intellectual disability (formerly called ''mental retardation'') ...

Epidemiology

Triploidy affects approximately 1–2% of pregnancies, but most miscarry early in development. At birth, males with triploidy are 1.5 times more common than females.

References

External links

{{Medical resources , ICD10={{ICD10, Q, 92, 7 , ICD9={{ICD9, 758.5 , DiseasesDB=32658 , MeSH=D057885 , Orphanet=3376 Syndromes affecting the nervous system Rare syndromes Congenital disorders Syndromes affecting the heart