In cases of 22q11.2 deletion syndome (also known as DiGeorge syndrome and Velocardiofacial syndrome/VCFS), a small part of the 22nd chromosome is missing at conception (called a micro deletion). It affects every cell of the body, with over 190 known symptoms/anomalies associated with it. No two people are affected in the same way, often making diagnosis very difficult. It is second only to Down syndrome in occurrence. In spite of being relatively common, many medical professionals are unfamiliar with it.

Other similar diagnoses are 22q duplication and 22q distal deletion. Because of these closely-related conditions, we choose to use the inclusive nomenclature “22q.”