Summary about Disease
Triploidy is a rare chromosomal abnormality where a fetus has three sets of chromosomes (69) instead of the normal two (46). This occurs because of an error during fertilization. It is almost always fatal, with most affected pregnancies ending in miscarriage or stillbirth. Infants born with triploidy rarely survive beyond a few hours or days.
Symptoms
Symptoms vary depending on whether the extra set of chromosomes is of maternal (Diandric triploidy) or paternal (Digynic triploidy) origin, and the degree of mosaicism (some cells having a normal chromosome number). Common symptoms include:
Severe growth restriction (intrauterine growth restriction - IUGR)
Multiple birth defects: Heart defects, brain abnormalities (e.g., holoprosencephaly), kidney defects, spina bifida.
Syndactyly: Fused fingers or toes
Abnormal facial features: Wide-set eyes, low-set ears, cleft lip/palate.
Placental abnormalities: Large, cystic placenta (in partial molar pregnancy associated with paternal origin) or small, fibrotic placenta (associated with maternal origin).
Amniotic fluid abnormalities: Polyhydramnios (excessive amniotic fluid) or oligohydramnios (too little amniotic fluid).
Causes
Triploidy is caused by errors during fertilization that result in a fetus having 69 chromosomes instead of the normal 46. The common mechanisms include:
Dispermy: Fertilization of a single egg by two sperm. This accounts for the majority of triploidy cases. Usually paternal in origin.
Diploidy in the egg or sperm: An egg or sperm cell contains a complete set of 46 chromosomes instead of the normal 23 due to a failure in meiosis (cell division that creates egg/sperm cells).
Medicine Used
There is no medicine used to treat triploidy itself, as it is a chromosomal abnormality that is almost universally fatal. Management focuses on supportive care and managing any complications that arise during pregnancy or after birth, if survival occurs.
Is Communicable
No, triploidy is not communicable. It is a genetic abnormality that occurs during fertilization and is not caused by any infectious agent.
Precautions
Since triploidy is a random genetic event, there are no known precautions to prevent it from occurring. Genetic counseling may be beneficial for parents who have had a previous pregnancy affected by triploidy to discuss recurrence risks, although the risk is generally very low.
How long does an outbreak last?
Triploidy is not an outbreak-related disease. It is a sporadic genetic abnormality.
How is it diagnosed?
Triploidy can be diagnosed during pregnancy through:
Prenatal screening: Blood tests (e.g., maternal serum screening) and ultrasound during pregnancy can raise suspicion if certain markers are abnormal, such as elevated or decreased hormone levels or specific physical features.
Diagnostic testing: Chorionic villus sampling (CVS) or amniocentesis are used to obtain fetal cells for karyotyping or chromosomal microarray analysis (CMA) to confirm the presence of three sets of chromosomes.
Postnatal diagnosis: If the infant survives birth, diagnosis can be confirmed through karyotyping or CMA of a blood sample.
Timeline of Symptoms
Early pregnancy: Often, triploidy leads to early miscarriage.
Second trimester: If the pregnancy continues, severe growth restriction and multiple birth defects are usually evident on ultrasound. Placental abnormalities may also be noted.
At birth (if survival occurs): Infants born with triploidy have severe birth defects and typically die shortly after birth.
Important Considerations
Genetic Counseling: Is crucial for parents who have received a diagnosis of triploidy. This helps them understand the condition, recurrence risks (which are generally low, but should be discussed), and options for managing the pregnancy.
Pregnancy Management: The decision to continue or terminate the pregnancy is a personal one that should be made in consultation with medical professionals.
Emotional Support: Bereavement support is essential for families who experience a pregnancy loss or infant death due to triploidy.
Mosaic Triploidy: In rare cases, an individual may have mosaic triploidy, where some cells are triploid and others are normal. The severity of symptoms in mosaic triploidy depends on the proportion of triploid cells.