Recent molecular genetics research has established that most cases of velocardiofacial syndrome (VCF) and of DiGeorge syndrome result from a submicroscopic deletion at chromosome 22q11.2. The medical features of this disorder include hypocalcemia, immunodeficiency, cleft palate, subtle facial dysmorphism, ‘conotruncal’ cardiac malformations (e.g. truncus arteriosus, tetralogy of Fallot, interrupted aortic arch, and certain types of ventricular septal defects), and other congenital malformations. While none of these complications is found in all patients with the 22q11.2 microdeletion, each is sufficiently common to be considered part of the disorder's medical phenotype.