Also known as: DiGeorge syndrome FISH, VCFS FISH, 22q11.2 FISH« Back to test list
Deletions of the proximal long arm of chromosome 22 (22q) cause a characteristic syndrome of developmental delay and malformations. The syndrome is called Di George syndrome (DGS) or velo-cardio-facial syndrome (VCFS). The deletion may be too small to be seen by conventional chromosome studies. This test provides diagnostic information.
These mutations are often de novo, and would not increase the risk of this disorder in siblings or other relatives. However, a parent and other relatives may carry the same deletion and be at increased risk of having another affected child.
In an affected person, an abnormal result is diagnostic of this microdeletion syndrome. Further family studies may clarify the recurrence risk in relatives.
A normal result makes it unlikely that the patient has this disorder.
Fluorescent in situ hybridisation (FISH) analysis using probes located within 22q.
This test is usually requested by a paediatrician or clinical geneticist. A full karyotype is usually requested at the same time.
2-5 mL blood in lithium heparin. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare pathology collection centre.
To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.
We also recommend that the patient or another adult check the labelling of request forms and sample tubes.
If the clinical diagnosis is uncertain, it may be preferable to request a microarray study rather than this specific FISH test as a microarray screens for microdeletions and duplications across all chromosomes.