Contributor: Gordon K. Klintworth
Trisomy 18 (Edwards syndrome) is a chromosomal disorder caused by three copies of human chromosome 18. In this trisomy syndrome structures of the upper face are stickingly abnormal and affected individuals have microcephaly and a characteristic facies due to an abnormal development of the upper face (frawnlike ears, micrognathia, a narrow bifrontal diameter),  high arched palate, prominent occiput. In addition infants with this syndrome commonly have a low birth weight,  hypertonia, poor muscle development, hand flexion, overlapping of the second and fifth fingers, limited hip adduction, rocker-bottom feet, webbing of the toes and doriflexion of the short great toe. Other manifestations that may occur include spells of apnea, cardiac malformations, renal anomalies (horseshoe kidney, malformations of the collecting duct), pyloric stenosis, elevation of the dome of the diaphragm, Meckel diverticulum and failure to thrive. Most cases die <1 year of age.
Common ophthalmologic abnormalities involve the eyelid [abnormal  palpebral fissures (short slanted palpebral fissures), epicanthal fold, blepharoptosis], orbit (hypoplastic orbital ridges, hypertelorism), cornea (corneal opacities, microcornea), lens (congenital cataract [cataract - congenital]), depigmentation of the retina, microphthalmos, congenital glaucoma [glaucoma - congenital], a uveal coloboma [coloboma - uvea] and cyclopia can also occur.