DiGeorge Syndrome is a congenital immunodeficiency due to defects in the T lymphocytes development caused by aplasia/hypoplasia of the thymus.
Synonyms: 22q11 Microdeletion syndrome, 22q11.2 deletion syndrome, CATCH-22 (CATCH 22) syndrome, Velocardiofacial syndrome & Congenital thymus aplasia
ICD: 10-CM D82.1
Epidemiology:
- Incidence: 1 per 4000 to 1 per 7000 births.
- Prevalence: True prevalence can only be determined by uniform newborn screening.
- Course: can be severe/life long or subside after few months in the neonate
Etiology:
- In most of the cases→ New mutation→ Microdeletion of 22q11 (MC microdeletion syndrome in humans)
- In 7% of cases AD inheritance from parents (parents with 22q11.2 deletion have a 50% risk of transmitting the deletion)
Pathogenesis: Microdeletion of 22q11 (22q11.2)→Maldevelopment of the 3rd and 4th pharyngeal arches and their associated pharyngeal pouches.→ hypoplasia of parathyroid glands and thymus, Facial Dysmorphism and Congenital Heart Defects.
Presentation (with varying severity) :

1. Primary Cellular immunodeficiency	Thymic hypoplasia→ T cell deficiency → Cellular immunodeficiency → Recurrent fungal and viral infections.
2. Hypocalcemia	Hypoplasia of parathyroid →hypoparathyroidism →hypocalcemia →Tetanic Convulsion
3. Cardiac & Vascular malformations	3rd and 4th pharyngeal arches maldevelopment → Fallot tetralogy, VSD, aberrant subclavian artery
4. Facial Dysmorphism	Disruption the 1st and/or 2nd arches→ fishy Mouth, Dysplastic Ears, Micrognathia, Cleft palate, Broad and Short Nose, Antimongoloid lid Axes, hypertelorism & hearing loss (malformation of ossicles)

Dx:
- Age of Dx: Severe cases with serious congenital cardiac defects or hypocalcemia are likely to be diagnosed in the neonatal period & mild cases with defects like submucous cleft palate or minimal facial anomalies are diagnosed later in childhood.
- CBC: low and T-cell count
- Other immuno-Dx: lymphocyte phenotyping & Lymphocyte proliferation testing
- Serum calcium
- Echocardiogram: CVS malformation
- Genetic testsing:2 status
Therapy (based on its severity):
- Infections: antibiotics and antimycotics
- Hypocalcemia: Cholecalciferol
- Severe immunodeficiency: Bone Marrow transplant & Thymus transplant (optional) to establish functioning immune cells
- Severe CVS & facial defects: surgery

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CATCH 22. Matsuo N, Yamagishi H. Ryoikibetsu Shokogun Shirizu. 2000;(30 Pt 5):150-3.
Chromosome 22q11.2 deletion syndrome: DiGeorge syndrome/velocardiofacial Syndrome. Sullivan KE. Immunol Allergy Clin North Am. 2008 May;28(2):353-66.
Transient neonatal hypocalcemia. Onset Manifestation of the 22q11.2 deletion syndrome. Pusceddu M, Bertone A, Campra D, Pontoriero D, Guala A. Minerva Pediatr. 2002 Aug;54(4):343-5.
DiGeorge anomaly in the absence of chromosome 22q11.2 deletion. Rope AF, Cragun DL, Saal HM, Hopkin RJ. J Pediatr. 2009 Oct;155(4):560-5.