DiGeorge syndrome and related syndromes associated with 22q11.2 deletions. A review.

DiGeorge syndrome (DGS) is a developmental defect which associates hypo- or aplasia of the thymus and parathyroids, facial dysmorphism and conotruncal cardiac malformations. The etiological factor in a great majority of DGS patients is monosomy for the 22q11.2 chromosomal region either through a large interstitial deletion of that region (inherited or de novo) or through an unbalanced translocation involving chromosome 22. In one instance, a balanced translocation of chromosome 22 was associated with a DGS phenotype. Extensive analyses of this region of chromosome 22 has led to the obtention of precise physical maps of the corresponding genomic region, to the cloning of the balanced translocation breakpoint and to the isolation of different genes from the minimal critical deleted region.