DiGeorge syndrome, also called 22q11.2 deletion syndrome, ******results from a microdeletion in a portion of chromosome 22 that leads to a developmental defect in the third pharyngeal pouch and third branchial cleft. One of the consequences of this is incomplete development of the thymus gland. An underdeveloped thymus gland results in an inability to create functional T cells.

Features of DiGeorge syndrome can be remembered with the CATCH-22 mnemonic:

• C – Congenital heart disease - Aortic arch defects
• A – Abnormal facies (characteristic facial appearance)
• T – Thymus gland incompletely developed
• C – Cleft palate
• H – Hypoparathyroidism and resulting Hypocalcaemia
• 22nd chromosome affected