DiGeorge / 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome is a genetic condition in which a small piece of one copy of chromosome 22 is missing. In most people the missing segment is about 2.5 to 3 million base pairs long and contains about 50 protein-coding genes; a smaller number of people have a shorter deletion. Loss of one gene in the region, TBX1, is thought to explain many of the typical physical features. Older names describe the same deletion seen through different specialties: DiGeorge syndrome (thymus, parathyroid and heart findings) and velocardiofacial syndrome (palate, heart and facial findings). Mechanism for nursing: the deleted genes affect early development of the heart's outflow tract, the thymus, the parathyroid glands and the palate. Three nursing consequences follow. A small or absent thymus means fewer mature T cells, so infection risk and live-vaccine safety depend on how many functioning T cells the person has. Small or poorly functioning parathyroid glands mean low parathyroid hormone, which causes hypocalcemia, especially during illness, surgery, puberty, pregnancy or childbirth. Conotruncal heart defects such as tetralogy of Fallot, interrupted aortic arch and ventricular septal...