DIGEORGE SYNDROME (DGS)

This disorder is characterized by (1) low blood calcium levels (hypocalcemia) due to underdevelopment (hypoplasia) of the parathyroid glands needed to control calcium; (2) underdevelopment (hypoplasia) of the thymus, an organ behind the breastbone in which lymphocytes mature and multiply; and (3) defects involving the outflow tracts from the heart. Most cases of DGS are due to a very small deletion (microdeletion) in chromosome band 22q11.2. A small number of cases have defects in other chromosomes, notably 10p13. Named after the American pediatric endocrinologist Angelo DiGeorge. Other names for DGS include hypoplasia of the thymus and parathyroids and the third and fourth pharyngeal pouch syndrome.