22q11.2 deletion syndrome
Updates to Article Attributes
22q11.2 deletion syndrome, also known as the DiGeorge syndrome or velocardiofacial syndrome, is a syndrome where a small portion of the chromosome 22 is lost and results in a variable but a recognisable pattern of physical and behavioural features.
Epidemiology
The estimated incidence is at ~ 1 in 4000-6000 live pregnancies 4,10.
Clinical presentation
CATCH 22 is the mnemonic to remember the chromosome and all the abnormalities.
- cleft lip +/- palate
- congenital heart disease (particularly conotruncal anomalies): often a major part of this syndrome
- characteristic facies
- elongated face
- short philtrum
- facial asymmetry
- prominent nose
- hypernasal speech
- learning disabilities
- decreased immunity
- malformation of third and fourth pharyngeal pouches that result in the defective development of the parathyroid and thymus which can, in turn, lead to
Pathology
Genetics
There is a near-universal association with a deletion within chromosome 22q11.2. The majority of cases have de novo mutations. 22q11 deletions are associated with some types of conotruncal cardiac defects as well as conotruncal anomaly face syndrome 5.
Associations
Radiographic features
Temporal bone malformations are common: 7:
- lateral semicircular canal dysplasia with small or absent bony island, forming a wide or single cavity with the vestibule (42% and 26%, respectively)
- cochlear incomplete partition type II (32%)
- middle ear ossicles
- dense stapes superstructure (39%)
- malleus, incus, or other stapes abnormalities (7%)
- carotid canal dehiscence (10%)
Brain and cerebrovascular malformations are common 6,8:
- persistent cavum septi pellucidi and/or cavum vergae (19-33%)
- aberrant cortical veins (25%)
- polymicrogyria or cortical dysplasia (17%)
- white matter hyperintensities (10%)
- hypoplastic internal carotid artery (8%)
- brain volume loss, most pronounced in the cerebellum (see hypoplastic cerebellum) 9
Cardovascular, particularly conotruncal, defects are usually the first imaging abnormality noted in these patients 10:
- cardiac anomalies
- tetralogy of Fallot and variants (35%)
- interrupted aortic arch (type B) (19%)
- truncus arteriosus (9%)
- ventricular septal defect (16%)
- atrial septal defect (2%)
- transposition of the great arteries (2%)
- vascular anomalies
- right aortic arch (35%)
- vascular ring (5%)
- aberrant origin of subclavian artery (16%)
- mirror image brachiocephalic vessel branching (12%)
- left superior vena cava (9%)
History and etymology
First described in 1968 by Angelo DiGeorge (1921-2009), an American physician.
-<a title="Right aortic arch" href="/articles/right-sided-aortic-arch-2">right aortic arch</a> (35%)</li>- +<a href="/articles/right-sided-aortic-arch-2">right aortic arch</a> (35%)</li>
-<a title="Vascular rings and slings" href="/articles/vascular-rings-and-slings">vascular ring</a> (5%)</li>-<li>-<a title="Aberrant right subclavian artery" href="/articles/aberrant-right-subclavian-artery">aberrant origin of subclavian artery</a> (16%)</li>- +<a href="/articles/vascular-rings-and-slings">vascular ring</a> (5%)</li>
- +<li>aberrant origin of subclavian artery (16%)</li>
-<a title="Left superior vena cava" href="/articles/left-sided-superior-vena-cava-1">left superior vena cava</a> (9%)</li>- +<a href="/articles/left-sided-superior-vena-cava-1">left superior vena cava</a> (9%)</li>