22q11.2 deletion syndrome is a genetic defect, resulting in variable phenotypes including DiGeorge or Shprintzen syndrome. Clinical manifestations may vary, including defects in the cardiovascular system (mostly conotruncal origin), thymus hypoplasia, and velo-pharyngeal malformations. Patients may suffer from neurodevelopmental disorders, including intellectual deficiencies and psychiatric conditions.

Prevalence of 22q11.2 deletion syndrome is approximately 1 in 4,000 live births, making it the most common form of chromosomal microdeletion disorders. The various deformities are a result of prenatal abnormalities of the third and fourth pharyngeal pouches and third branchial arch. Cardiac defects are usually of conotruncal origin, such as tetralogy of fallot, aortic arch interruption, ventricular septal defect (VSD) or persistent truncus arteriosus. Developmental defects of the thymus often lead to T-cell related immunodeficiency, which may be present in 25-30 % of the patients. Affection of the parathyroid glands may lead to hypocalcaemia, presenting as tetany or seizures.

Various neurodevelopmental or psychiatric disorders may be present, ranging from mild cognitive impairment to recurrent episodes of schizophrenia, manifesting as early as childhood or puberty. Velopharyngeal anomalies are common, resulting in an increased probability of cleft lip and palate, as well as choanal atresia or various nasal breathing obstructions. Pharyngeal insufficiency may lead to reflux and feeding difficulties especially in infancy. Laryngeal webs may also be associated with the disorder.

Other features may include renal malformations, hearing loss and skeletal deformities such as scoliosis or cervical spine abnormalities.