The systemic effects of 22q11.2 deletion syndrome on immunity.

22q11.2 deletion syndrome (22q11.2DS) affects about 1/2,150 individuals, causing complex and variably penetrant clinical problems. The clinical phenotypes evident at birth can include thymic hypoplasia, hypoparathyroidism, heart defects, and/or facial dysmorphism. Neurological issues including behavioral problems such as autism spectrum disorders and schizophrenia are evident at later postnatal periods. Thymic hypoplasia affects about 60-70% of patients, leading to T cell lymphopenias of varying severity. In rare cases, a congenital athymia occurs, necessitating a thymic implant. This review provides information regarding the causes and consequences of 22q11.2DS on thymic functions along with its broader impacts on the immune system. The affected immune cells include T, B, and mast cells. Patients with 22q11.2DS have more infectious, autoimmune, and allergic complications. Broader systemic changes including increased vascular permeability, a disrupted blood-brain barrier, and epigenetic alterations resulting from deletions on chromosome 22q11.2 affect many organ systems that can involve immune responses.