22q11.2 Syndrome, previously known as DiGeorge Syndrome or Velocardiofacial Syndrome, is an immunodeficiency that is caused by a microdeletion of chromosome 22. DiGeorge and Velocardiofacial Syndrome were historically named differently, but are now understood to be phenotypic presentations of the same disorder.
A 22q11.2 microdeletion leads to a developmental failure of the 3rd and 4th pharyngeal pouches, which includes the thymus and parathyroid glands.
Patients have thymic aplasia and T-cell deficiency, with increased susceptibility to viral/fungal infections. Patients also have parathyroid dysplasia and subsequent hypoparathyroidism, causing hypocalcemia.
Other findings include abnormal facies including cleft palate. Cardiac involvement typically includes truncus arteriosus and Tetralogy of Fallot. Diagnostic confirmation requires the FISH technique to locate the microdeletion.
Find DiGeorge Syndrome and more Immunodeficiencies among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.