Chromosome 18p deletion syndrome / De Grouchy syndrome 1/ 18p minus syndrome/ Monosomy 18p.
Incidence
Monosomy 18p is usually caused by spontaneous (de novo) errors very early in the development of the embryo that appear to occur randomly for unknown reasons (sporadically).
Clinical Characteristics
It is one of the most frequently occurring chromosomal aberrations with minimal abnormalities visible at birth, which become more apparent at the age of three years. Chromosome 18, Monosomy 18p is a rare chromosomal disorder in which all or part of the short arm (p) of chromosome 18 is deleted (monosomic). The disorder is typically characterized by short stature, variable degrees of mental retardation, speech delays, malformations of the skull and facial (craniofacial) region, and/or additional physical abnormalities. Associated craniofacial defects may vary greatly in range and severity from case to case. However, such features commonly include an unusually small head (microcephaly); a broad, flat nose; a \\\"carp-shaped\\\" mouth; large, protruding ears; widely spaced eyes (ocular hypertelorism); and/or other abnormalities. 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).
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. All or part of the short arm (p) of chromosome 18 is deleted.