De Grouchy syndrome type 1

Deletion of the short arm of chromosome 18. It is one of the most fre quently occurring chromosomal aberrations with minimal abnormalities visible at birth, which become more apparent at the age of three years. The phenotype is marked mainly by holoprosencephaly, brachycephaly, broad facies, blepharoptosis, downturned corners of the mouth, tooth abnormalities, broad neck with low posterior hairline, funnel chest, enlarged labia majora, hand abnormalities, mental retardation ranging from mild to severe, and other malformations. The phenotype varies from case to case, frequently reflecting the length and type of deletion: del(18p) mosaicism is associated with abnormalities which are similar to those in del(18p) and include microphthalmia and cataract and cyclopia may occur in del(18p) in mosaicism with dup(18p).