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constitutional triploidies

Wednesday 12 January 2005

Definition: Triploidy is the presence of an additional haploid set of chromosomes, is the cause of 20% of spontaneous abortions, premature births and perinatal deaths.

Triploidy syndrome is a rare syndrome and is estimated to occur in about 2 per cent of conceptuses. Triploidy occurs when there is double fertilization of an ovum (dispermy). The result may be 69, XXX or 69, XXY or 69, XYY. The extra set of paternal chromosomes predisposes to formation of a partial mole, features of which may or may not be grossly or microscopically apparent.

The survival of individuals with diploid/triploid mixoploidy is usually longer than of those with pure triploidy.

Types

- 69,XXX triploidy
- 69,XXY triploidy
- 69,XYY triploidy

Physiopathology

Triploidy is constituted by an extra haploid set of chromosomes for a total of 69 chromosomes in humans. A "parent-of-origin" effect has been demonstrated by analysis of cytogenetic polymorphisms of triploidy pregnancies. Two distinct phenotypes of human triploid fetuses have been recognized according to the parental origin of the extra haploid set.

The first one or triploidy of diandric type occurs when the extra haploid set of chromosomes arises from the father, the second one or triploidy of digynic type occurs when the extra haploid set of chromosomes arises from the mother. Diandric fetuses appear relatively well grown with a large placenta, while digynic fetuses show intrauterine growth retardation with a small placenta.

Types

- maternal triploidy (triploidy by digyny)
- paternal triploidy (diandry or dispermy)

  • embryonal mole or partial mole
    • pseudomolar placenta

Synopsis

The most common clinical signs of triploidy are: severe intrauterine growth retardation, macrocephaly, total syndactyly of third and fourth fingers and CNS, heart and renal defects.

Hydatidiform mole, one of the characteristic features of pure triploidy, is found in more than 90% of cases.

The spectrum of external malformations included a dysmorphic face (broad root of the nose, exophthalmos, low-set ears, micro-/retrognathia, microgenia, median cleft lip and/or palate, gnathoschisis, macroglossia), encephalocele, spina bifida, syndactyly, club or rocker-bottom feet, pes equino-valgus. More common internal malformations included ventricular septum defect of the heart, abnormal lobation of the lungs, and renal disease (agenesis, cysts).

- systemic anomalies

  • general dysmaturity
  • muscular hypotonia
  • prematurity
  • fetal growth failure
  • IUGR (intra-uterine growth retardation)

- craniofacial anomalies

  • broad root of the nose
  • exophthalmos
  • low-set ears
  • micrognathia
  • retrognathia
  • microgenia
  • median cleft lip
  • median cleft palate
  • gnathoschisis
  • macroglossia
  • large posterior fontanel
  • incomplete ossification of calvaria
  • low-set ears
  • ear malformations, dysmorphic auricles
  • low-set malformed ears
  • hypertelorism
  • prominent forehead
  • micrognathia
  • dysplastic cranial bones
  • hypertelorism
  • cleft lip, cleft palate
  • macroglossia
  • large nose, bulbous nose

- ocular anomalies

  • microphthalmia
  • iris coloboma

- cardiopulmonary malformations

  • cardiac malformations
  • pulmonary lobation anomalies

- digetsive malformations

- adrenal hypoplasia

- limb anomalies

  • syndactyly of third and fourth fingers
  • camptodacyly
  • single palmar crease
  • talipes equinovarus
  • proximal displacement of thumbs

- genito-urinary malformations

  • renal hypoplasia
  • fetal renal cysts
  • fetal hydronephrosis
  • hypospadias
  • cryptorchidism
  • external genitalia misdevelopment
  • hypogonadism
  • testicular Leydig cell hyperplasia
  • micropenis
  • bifid scrotum
  • ovarian hypoplasia

- omphalocele

- cerebrospinal anomalies

  • hydrocephalus
  • Arnold-Chiari malformation
  • lumbosacral myelomeningocele
  • holoprosencephaly
  • hypoplasia of basal ganglia
  • cerebellar hypoplasia
  • occipital lobe hypoplasia
  • corpus callosum agenesis

- placental anomalies

  • partial hydatiform mole
  • mild trophoblastic proliferation
  • hydropic villi with scalloping
  • large cisternae within villi
  • trophoblastic inclusions
  • large placenta with placental hydatidiform changes

- maternal anomalies

  • midtrimester preeclampsia
  • polyhydramnios
  • proteinuria
  • arterial hypertension

See also

- chromosomes

  • chromosomal anomalies
  • chromosomal diseases

- malformative syndromes

References

- Sergi C, Schiesser M, Adam S, Otto HF. Analysis of the spectrum of malformations in human fetuses of the second and third trimester of pregnancy with human triploidy. Pathologica. 2000 Aug;92(4):257-63. PMID: 11029886