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

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

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, and covering a surface. Mosaics are often used as floor and wall decoration, and were particularly pop ...

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 and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

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 develop into two hemispheres, typically occurring between the 18th and 28th day of gestation. Normally, the forebrain is formed an ...

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary inc ...

(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 Chiari malformation (CM) is a structural defect in the cerebellum, characterized by a downward displacement of one or both cerebellar tonsils through the foramen magnum (the opening at the base of the skull). CMs can cause headaches, difficu ...

, agenesis of the corpus callosum and

neural tube defect Neural tube defects (NTDs) are a group of birth defects in which an opening in the spine or cranium remains from early in human development. In the third week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo b ...

s. Skeletal manifestations include

cleft lip/palate 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 nose. The te ...

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 as ...

club foot Clubfoot is a birth defect where one or both feet are rotated inward and downward. Congenital clubfoot is the most common congenital malformation of the foot with an incidence of 1 per 1000 births. In approximately 50% of cases, clubfoot aff ...

and

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δά� ...

of fingers three and four.

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

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

omphalocele Omphalocele or omphalocoele also called 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 loops out of ...

and meningocele (

spina bifida Spina bifida (Latin for 'split spine'; SB) is a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy. There are three main types: spina bifida occulta, men ...

) are also common. Cystic hygromas occur but are uncommon. Triploid fetuses have

intrauterine growth restriction Intrauterine growth restriction (IUGR), or fetal growth restriction, refers to poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's ...

beginning early in the pregnancy, as early as 12 weeks, and does not affect the head as severely as the body. Oligohydramnios, 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 to look out for include but are not limited to swelling, edema, or hypertension. 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 nose. The te ...

, 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 fertilizing one egg ( polyspermy) (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 stan ...

, 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 A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes). Description and causes Most organisms that reprodu ...

and

trisomy 18 A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes). Description and causes Most organisms that reprodu ...

, which may appear similar on sonography. Genetic testing 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 (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...

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, a life-threatening condition, or

choriocarcinoma Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs. It belongs to the malignant end of the spectrum in gestational trophoblastic disease (GTD). It is also c ...

, 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, and covering a surface. Mosaics are often used as floor and wall decoration, and were particularly pop ...

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 or cognitive deficits, including intellectual disability (formerly called ''mental retardation''), deficits too mild to pr ...

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