Chromosome 18q duplication syndrome. 18q+ syndrome. Trisomy 18q.
Incidence
Very rare syndrome. Sporadic.
Clinical Characteristics
Duplication of the long arm of chromosome 18 with variable abnormalities, including intra-uterine growth retardation; characteristic facies with malformed ears, micrognathia, and prominent occiput; heart malformations; and psychomotor retardation. The phenotype in duplication of the long arm of chromosome 18 is similar to that in trisomy 18. The proximal segment of 18q(18q11) appears to be crucial for the expression of most characteristics of the phenotype. Duplication of the middle segment [18q(18q12-q21)] has some minimal phenotypic effects. Duplication of the distal segment [18q(18q22-18qter)] has a somewhat greater influence on the expression. dup(18q)q21) is associated with a majority of symptoms, but the full range of the phenotype is observed in dup(18q)(q1-qter).
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. Duplication of the long arm of chromosome 18.