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Fetopathology and developmental pathology of the embryo and fetus
Marta Ježová, Josef Feit et al.
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Triploidy
Marta Ježová
Etiology, pathogenesis

Karyotype is 69 XXY, 69 XXX or 69XYY

3 possible mechanisms:

  • Dispermia: fertilization of haploid egg by two sperms (most common)
  • Diandria: fertilization of haploid egg by diploid sperm
  • Digynia: fertilization of diploid egg by haploid sperm

The extra chromosomal set can either be of a paternal (dispermia, diandria) or maternal (digynia) origin. The development of both the fetus and the placenta is seriously affected. Basically the extra paternal chromosome set leads to an abnormal placental overgrowth  — molar placenta (partial mola hydatidosa) the embryo becomes stunted and is aborted early in the first trimester.

In cases with extra maternal set of chromosomes the placenta is extremely small, nonmolar. The fetus with marked intrauterine growth retardation and congenital malformations is aborted late in second or third trimester.

Clinical signs
  • Triploidy is one of the most frequent chromosomal aberrations in humans and the most frequent chromosomal abnormality in the first trimester abortions.
  • The risk does not increase with advanced maternal nor parental age
  • Triploidy is lehtal, most affected fetuses are spontaneously aborted or stillbirth
  • Livebirth is extremely rare, death occurs within a few hours after birth
  • Marked intrauterine growth retardation is a cardial feature of triploidy
Macroscopic appearance
  • External features: macrocephaly, disproportionally large head, hypertelorism, large bulbous nose, low set malformed ears, micrognathia, talipes equinovarus, short and proximally displaced thumbs, syndactyly between the third and fourth fingers, simian crease
  • Cardiovascular malformations: in 20% of the cases namely ventricular septal defect
  • CNS malformations:hydrocephalus, Dandy Walker malformation, rarely holoprosencephaly
  • Adrenal hypoplasia, pulmonary hypoplasia, thymus hypoplasia, malrotation of colon
  • Single umbilical artery
  • Abnormal placenta see above
Prenatal diagnosis
  • clinical features of triploidy overlap with those of the other chromosomal aberration syndromes trisomy 18 especially
  • marked intrauterine growth retardation and relative macrocephaly might be the only abnormalities detected,serious internal malformations may be absent
Triploidy Triploidy
Pictures

Stillborn 33-week triploid (69 XXX) macerated fetus, markedly growth retarded, weight 580 g (normal weight should be 1500 g), macrocephaly, low set ears, bulbous nose: Triploidy, face stigmatisation, Macro, autopsy (72449) Triploidy, stigmata, Macro, autopsy (72451)

Upper limb, syndactyly of fingers 3 and 4 (the same case): Triploidy, Macro, autopsy (72450)

Placenta is extremely small for gestational age, nonmolar (weight 58g, normal cca 300g): Triploidy, small placenta, Macro, autopsy (72452)

Another case of a triploid fetus with growth retardation, macrocephaly, micrognathia: Triploidy, Macro, autopsy (72984) Triploidy, Macro, autopsy (72985) Triploidy, Macro, autopsy (72986)