trisomy 18
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Definition: Trisomy 18 (1/5000 live births) presents with a great phenotypic variability. Intrauterine growth retardation (IUGR) with normal or increased amniotic fluid volume, craniofacial dysmorphism (strawberry-shaped head, micrognathia, choroid plexus cyst), congenital heart disease, omphalocele, large cisterna magna, and abnormal extremities (clenched hands and rocker-bottom feet) are frequently observed anomalies.
At least 30% of affected fetuses have abnormal extremities (unilateral or bilateral), the most frequent one being clenched hand and radial aplasia.
Synopsis
systemic anomalies
- intra-uterine growth retardation (IUGR)
- low feat activity
- polyhydramnios
- failure to thrive
placental anomalies
- small placenta
- single umbilcal artery
cardiovascular anomalies
craniofacial anomalies
- short eyelid fissures
- small mouth
- small jaw
- microcephaly
- epicanthal folds
- low set malformed ears
- ceft lip/palate
- eye abnormalites (10%)
limb anomalies
- clenched hand: clenched fists with the index finger overlapping the 3rd and 4th fingers
- absence of the distal crease on the 5th finger
- low-arch dermal ridge pattern on the fingertips
- nails underdeveloped
- big toe shortened and bent backward (dorsiflexed)
- underdeveloped or absent thumbs
- bilateral club feet
- rocker-bottom feet
- webbed fingers and toes (syndactyly)
- radial aplasia (5-10%)
- arthrogryposis (joint contractures)
- diaphragmatic anomalies
- renal malformations
- pulmonary malformations
- pulmonary lobar anomalies
redundant skin folds
cryptorchidism
spina bifida (6%)
scoliosis
omphalocele
Cantrell pentalogy (3232702)
Epidemiology
Prevalence (Since 1961)7 studies: 1/3400 - 1/11000
1-5000 liveborn
1-5000 stillborn
20 - 30% die in the first month
90% die by age one
Cytogenetics
trisomy - 95%
translocation - 2%
mosaic - 3%