Duplication of the 22q11.2 region associated with congenital cardiac disease.

The DiGeorge, or velocardiofacial, syndrome has been aetiologically linked to heterozygous deletion of the q11.2 region of chromosome 22. It is the most common of the microdeletion syndromes, and is associated with malformations involving the ventricular outflow tracts. Duplication of the 22q11.2 region has also been reported, adding to a growing list of syndromes involving genomic deletion or duplication that cause disease by decreasing or increasing the gene dosage. We report two cases of congenital cardiac disease associated with microduplications of 22q11.2, and discuss the evidence to date for the potential clinical significance of this genetic defect.