22q11.2 deletion syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2] Ayushi Jain, M.B.B.S[3]
Overview
22q11.2 deletion syndrome is a disorder caused by the deletion of a small piece of chromosome 22. The deletion occurs near the middle of the chromosome at a location designated q11.2. DiGeorge Syndrome (DGS) is a combination of signs and symptoms caused by defects in the development of structures derived from the pharyngeal arches during embryogenesis.
It comprises of thymic hypoplasia, hypocalcaemia, outflow tract defects of the heart, and dysmorphic facies.
Historical Perspective
DGS characteristics were first described in 1828 but adequately reported later in 1965 by Dr. Angelo DiGeorge, as a clinical trial that included immunodeficiency, hypoparathyroidism, and congenital heart disease.
Historically, DGS was grouped within a sphere of other syndromes such as Shprintzen-Goldberg syndrome, velocardiofacial syndrome, Cayler cardiofacial syndrome, Sedlackova syndrome, conotruncal anomaly face syndrome, and DGS, collectively called 22q11 deletion syndromes. They have the same genetic etiology but their varying phenotypes has has led to confusion in diagnosing patients with DGS, which causes potentially catastrophic delays in diagnosis.
Classification
There is no established system for the classification of DGS.
Pathophysiology
The main factor leading to DGS is the deletion of 22q11.2, which encodes over 90 genes.
The 22q11.2 deletion syndrome can be inherited in an autosomal dominant manner. Prenatal testing, such as amniocentesis, is available for pregnancies determined to be at risk. Also pregnancies who have findings of congenital heart disease and/or cleft palate detected by ultrasound examination may be offered prenatal testing. Genetic counseling may be helpful for families who may have DiGeorge syndrome. Because most of the signs of this cluster of defects can also be inherited as autosomal recessive or x-linked traits, only genetic testing of both parents can determine with any certainty the likelihood these anomalies occurring in any subsequent children.
Causes
Most cases are linked to microdeletion of chromosome 22, at the long arm (q) at the 11.2 locus.
Differentiating [Disease] from Other Diseases
Epidemiology and Demographics
22q11.2 deletion syndrome affects an estimated 25 in 100,000 live births. Microdeletion of 22q11.2 is the most common microdeletion syndrome, affecting approximately 0.1% of fetuses. The rate of 22q11.2 microdeletion in live births occurs at an estimated rate of 1 in 4000 to 6000.[1]
Risk Factors
The only known risk factor is that of a family history of DGS.
Screening
Natural History, Complications, and Prognosis
Natural History
Complications
Prognosis
Diagnosis
Diagnostic Criteria
History and Symptoms
Physical Examination
Laboratory Findings
Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Prevention
References
- ↑ McDonald-McGinn DM, Sullivan KE, Marino B, et al. 22q11.2 deletion syndrome. Nat Rev Dis Primers. 2015;1:15071. Published 2015 Nov 19. doi:10.1038/nrdp.2015.71