The 22q11.2 deletion syndrome is the most common microdeletion disorder with an estimated prevalence of 1 in 3000-6000 live births. Most of the patients show the common 3 Mb deletion, but proximal 1.5 Mb deletion and unusual deletions located outside the common deleted region, have been detected. Various syndromes have been associated with 22q11.2 deletion including DiGeorge syndrome (DGS), velocardiofacial syndrome (VCFS), conotruncal anomaly face syndrome (CTAF), and isolated and familial forms of cardiovascular malformation. Microdeletions of 22q11.2 have been found in more than 90% of patients with DGS and over 85% of VCFS/ CTAF patients. In addition, several patients with Opitz-GBBB syndrome have been reported with microdeletions of 22q11. The variability in the clinical expression of this disease is extremely wide. Classical features include congenital heart disease, velopharyngeal insufficiency or cleft palate, facial anomalies, speech and learning disabilities, neonatal hypocalcemia, and T-cell immune deficit. Nevertheless, the spectrum of anomalies associated with 22q11.2 deletion is becoming wider and wider. Some cardiovascular abnormalities are relatively specific for the syndrome. An interruption of the aortic arch, type-B (IAA-B) is associated with deletion 22q11 in approximately 50% of cases. Other defects including tetralogy of Fallot [DS:H00549], double outflow right ventricle, ventricular septal defect and an aberrant origin of the right subclavian artery are frequently found.
