Trisomy 18 (Edwards)

• 30/% die within 2 mos, 95% die by 1 year of age; long term survivors may have mosaicism
• 1 in 5000 live births; mostly females 4:1
• associated w/ advanced maternal age

• Risk of recurrence after one affected child with a standard trisomy is 1% for a baby with some form of trisomy (trisomy 21 would be the most common)

Characteristics

• Development: mental retardation
• General: hypertonic
• Head: micrognathia, prominent occiput, narrow palpebral fissueres, low set/malformed ears
• Chest: short sternum, congenital heart disease
• Hands: flexion deformities, nail hypoplasia, index and pinky fingers overlap the middle two (mnemonic: 18 year old showing funky gang sign)
• Feet: rocker-bottom deformity (convex sole, prominent heel), caused by vertical talus.
• Cryptorchidism, horseshoe kidney
• Cutis Marmorata
• 10-20% have cleft lip, exomphalos, or radial aplasia.

Some differences between Trisomy 13 and 18

• Both can have rocker bottom feet.
• 18 is hypertonic
• Head: 18 has micrognathia, prominent occiput. 13 has aplasia cutis and low hairline
• Hands: 18 has nail hypoplasia, index and pinky fingers overlap the middle two (mnemonic: 18 year old showing funky gang sign); 13 has polydactyly

Trisomy 13 (Patau)
Trisomy 21 (Down)

CHLA board review course 2005
Baraitser and Winter, 1996. Color Atlas of Congenital Malformation Syndromes