Triploidy

Disease Overview

Summary

Triploidy is a rare chromosomal abnormality. Triploidy is the presence of an additional set of chromosomes in the cell for a total of 69 chromosomes rather than the normal 46 chromosomes per cell. The extra set of chromosomes comes either from the father or the mother during fertilization. Pregnancies with triploidy are usually miscarried early in the pregnancy. If the pregnancy continues to term, the infant dies within the first days of life. A few affected individuals have been reported to have survived to adulthood, but had developmental delay, learning difficulties, seizures, hearing loss and other abnormalities. Individuals who survive have mosaic triploidy, meaning that some cells have the normal number of 46 chromosomes and other cells have 69 chromosomes per cell. Infants affected with complete triploidy have growth restriction and multiple birth defects.

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Synonyms

• chromosome triploidy syndrome
• Triploid syndrome
• triploidy syndrome

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Signs & Symptoms

Infants affected with triploidy have heart defects, abnormal brain development, adrenal and kidney defects (cystic kidneys), spinal cord malformations (neural tube defects) and facial differences (widely spaced eyes, low nasal bridge, low-set malformed ears, small jaw, absent/small eye and cleft lip and palate). The third and fourth fingers of the hands and the second and third toes of the feet may be united, and the hands may have unusual simian creases. There may also be liver and gallbladder defects, twisted intestines and deformities of the fingers and toes. The placenta in triploidy may be immature, large and filled with cysts. Individuals who are mosaic will survive longer than those with complete triploidy but usually have intellectual disability, developmental delay, depression, seizures, short stature, obesity and other abnormalities.

The pregnant mother carrying a fetus with triploidy sometimes has high blood pressure (hypertension), swelling (edema) and excretion of albumin in the urine (albuminuria). This condition is called toxemia or preeclampsia.

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Causes

Triploidy is the presence of a complete additional set of chromosomes. The triplication of the chromosomes is caused by the fertilization of an egg by two sperms, or the fertilization of an egg by a sperm that has an extra set of chromosomes or by the fertilization of an egg that has an extra set of chromosomes by a normal sperm. This disorder does not run in families and is not associated with maternal or paternal age.

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Affected populations

Triploidy occurs in about 1-3% of all pregnancies. About 2/3 of triploid pregnancies are male.

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Disorders with Similar Symptoms

Symptoms of the following disorders are caused by duplication, triplication or deletion of chromosomes:

Tetraploidy is a condition in which there are four sets of chromosomes in a single cell instead of the normal two sets. The total number of chromosomes per cell in tetraploidy is 92 instead of 46. These pregnancies usually miscarry early in the pregnancy or affected babies die within the first days of life. These children have been reported to have multiple birth defects as well as facial differences including small head and jaw, cleft lip and palate, small or absent eyeballs, abnormal ears, heart defects, brain defects, abnormal genitals and feet abnormalities (clubfoot). Tetraploidy can be suspected during pregnancy by the detection of birth defects on ultrasound. The diagnosis can be confirmed by a chromosome study of cells taken during pregnancy through amniocentesis or chorionic villus sampling (CVS).

Trisomies, such as trisomy 21 (Down syndrome), are characterized by a triple chromosome. The most common symptom of trisomies is intellectual disability. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males, and two X chromosomes for females. People with a trisomy have an extra chromosome added to one of the normal pairs. The triplication of the chromosome may be partial, either an extra short arm (p+) or an extra long arm (q+). Conditions are classified by the name of the abnormal chromosome pair and which portion of the chromosome is affected. (For more information on this disorder, choose “Trisomy” as your search term in the Rare Disease Database.)

Down syndrome (trisomy 21) is the most common and readily identifiable genetic condition caused by a chromosomal abnormality. One additional chromosome is present. Children with Down syndrome have some degree of intellectual disability that can range from mild to profound. Most children with Down syndrome function in the mild to moderate range.

Chromosome 11q-syndrome (Jacobsen syndrome) is a rare genetic disorder caused by lack of the long arm of chromosome 11. The disorder may be characterized by a narrow protruding forehead, eye problems, facial differences of the nose and mouth and intellectual disability. The severity and type of abnormality depends upon the size and location of the missing chromosome piece. The cause of this chromosome abnormality is unknown. (For more information on this disorder, choose “Chromosome 11, Partial Monosomy 11q” as your search term in the Rare Disease Database.)

Chromosome 18p-syndrome is a deletion of the short arm (p) of chromosome 18. It is characterized by unusual facial features and mild to severe intellectual disability. This syndrome may also include growth deficiency, diminished muscle tension and a smaller than normal sized brain. There may also be behavior problems and delayed speech. (For more information on this disorder, choose “Chromosome 18p-Syndrome” as your search term in the Rare Disease Database.)

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Diagnosis

The presence of multiple major malformations, low amniotic fluid and/or growth restriction on fetal ultrasound during pregnancy raises the suspicion of triploidy. The diagnosis can be made during pregnancy by chromosome analysis (karyotyping) of cells obtained by amniocentesis or chorionic villus sampling (CVS). The diagnosis can be confirmed after birth by chromosome analysis of tissue (skin) obtained from the affected infant. Triploidy cannot be diagnosed by chromosome microarray testing. The accuracy of non-invasive prenatal testing using cell-free fetal (cff) DNA in the diagnosis of triploidy is still being studied. Abnormal levels of specific maternal blood proteins such as alpha-fetoprotein, human chorionic gonadotropin, estriol and pregnancy-assisted plasma protein-A have been associated with an increased risk for triploidy.

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Standard Therapies

Treatment

Treatment of triploid syndrome is symptomatic and supportive.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

Some current clinical trials also are posted on the following page on the NORD website: https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/

For information about clinical trials sponsored by private sources, contact: www.centerwatch.com

For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/

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References

TEXTBOOKS
Jones KL, Ed. Smith’s Recognizable patterns of Human Malformation. 4th ed. W.B. Saunders Company. 1998:32-35.

JOURNAL ARTICLES
Toufaily MH, Roberts DJ, Westgate MN, Holmes LB. Triploidy: Variation of Phenotype. AM J Clin Pathol. 2016 Jan; 145(1):86-95. doi: 10.1093/ajcp/aqv012

Jewell R, BirchA, Roberts P, et al. Phenotypic features of diploid/triploid mosaicism in an adult. Clin Dysmorphol. 2014;23:56-59

Boonen SE, Hoffman AL, Donnai D, et al. Diploid/triploid mosaicism: a rare event or an under-diagnosed syndrome? Eur J Med Genet. 2011;54:374-375.

Benn PA, et al. Second trimester maternal serum analytes in triploid pregnancies: correlation with phenotype and sex chromosome complement. Prenat Diag. 2001;21:680-686.

Carp H, et al. Karyotype of the abortus in recurrent miscarriage. Fertil Steril 2001;75:678-682.

Zaragoza MV et al. Parental origin and phenotype of triploidy in spontaneous abortions: predominance of diandry and association with the partial hydatidiform mole. Am J Hum Genet. 2000;66:1807-1820.

Cerakushansky G, et al. Diploid/triploid mosacicism: Further delination of the phenotype. Am J Med Genet. 1994;52:399-401.

Graham JM, et al. Triploidy: Pregnancy complications and clinical findings in seven cases. Prenat Diag. 1989;9:409-19.

Edwards MJ, et al. Clinical features of diploid/polyploid mixoploidy in older individuals. Pediat Res. 1989;25:76.

Angell RR, et al. Chromosome studies in human in vitro fertilization. Hum Genet. 1986;72:333-339.

Doshi N, et al. Morphologic anomalies in triploid liveborn fetuses. Hum Path. 1983;14(4):716-723.

Graham JM, et al. Diploid-Triploid mixoploidy: Clinical and cytogenetic aspects. Pediatrics. 1981;68:23-8.

Beatty RA. The origin of human triploidy: An integration of qualitative and quantitative evidence. Ann Hum Genet (Cambridge). 1978;41:229-314.

Wertelecki W, et al. The clinical syndrome of triploidy. Obst Gyn. 1976;47:69-76.

INTERNET
Triploidy. Unique. Last Update 2005. https://www.rarechromo.org/media/information/Other%20Topics/Triploidy%20FTNP.pdf Accessed Feb 26, 2024.

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