Definition:

DiGeorge syndrome (DGS) is a primary immunodeficiency disease characterized by dysgenesis of the thymus and parathyroid glands, conotruncal cardiac anomalies, and other dysmorphic features. This syndrome is usually associated with hypocalcemia resulting from hypoparathyroidism. In most cases the initial symptom is tetany caused by hypocalcemia within 24-48 hours after birth, with symptoms by immune abnormality appearing later. Most patients with this syndrome have a genomic deletion of chromosome 22q11, including the DiGeorge critical region (DGCR). A small number of cases of DGS have defects in other chromosomes, notably 10p13. Approximately 17% of patients with the phenotypic features of this syndrome have no detectable genomic deletion. Several mutations in TBX1 have been identified recently in non-deleted patients, including missense and frameshift mutations.