Partial deletion of the long arm of chromosome 18 produces a syndrome marked by mental and growth retardation with hypo-tonia. The facies is striking with microcephaly, midface hypoplasia, a carplike mouth with downward slanting margins, and a prominent antihelix and/or antitragus of the ears with a narrow or atretic canal and hearing loss. Cardiac and genitourinary malformations are common. The fingers taper markedly with a high frequency of whorl patterns, and simian creases may be evident. Toes have abnormal placement with the third toe placed above the second and fourth. Dimples may be evident on knuckles, knees, elbows, and shoulders. Ophthalmic abnormalities include epicanthus, hypertelorism, downward slanting of the palpebral fissures, nystagmus, strabismus, corneal abnormalities, cataracts, blue sclerae, dys-plastic or atrophic optic nerve heads, and colobomatous microphthalmia.60-70'92'208'239'309'354'390
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