The syndrome caused by contiguous deletion of about 2.5 megabases (Mb) at position 11.2 on the long arm of human chromosome 22 produces includes the phenotypes described as Di George syndrome and velocardiofacial syndrome.
Epidemiology
22q11.2DS is rare, perhaps with an incidence of about 14 per 100,000 live births. It is reported to be the most common of the chromosomal microdeletion syndromes.
The syndrome
The common manifestations are:
- Cardiac abnormalities, 67% - primarily conotruncal defects (truncus arteriosus, tetrology of Fallot, transposition of the great arteries, etc).
- Palatal abnormalities, >65% - velopharyngeal incompletence, submucous cleft palate (and less frequently overt cleft palate).
- Characteristic facies, most individuals - ptosis, orbital hypertelorism, malar flatness, micrognathia.
- Immune deficiency, 77% - due to thymic hypoplasia.
- Developmental delay and intellectual disability, most individuals.
The phenotype may also include:
- Dental caries secondary to enamel hypoplasia.
- Gastrointestinal, renal, and musculoskeletal abnormalities.
- Hearing loss.
- Autoimmune disorders.
- Thrombocytopenia, haemolytic anaemia.
Diagnosis…
is by detection of a heterozygous deletion at 22q11.2, usually by chromosomal microarray or FISH. Specifically, the deletion is usually seq[GRCh37] del(22)(q11.2) chr22:18,912,231-21,465,672
Further reading
- McDonald-McGinn DM, Hain HS, Emanuel BS, et al. 22q11.2 Deletion Syndrome. 1999 Sep 23 [Updated 2024 May 9]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Link