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Williams Syndrome deletion 7q11.2 by FISH*

Test Code


Test Synonyms



Fluorescence in situ Hybridization (FISH)
*Performed by affiliate laboratory

Turnaround Time

7-9 days

Specimen Requirements

5mL peripheral blood in sodium heparin
3mL bone marrow in sodium heparin
Fixed cytogenetically prepared cells in sterile centrifuge tube with pellet visible in 3:1, Methanol:Acetic Acid

Specimen Stability
Blood and bone marrow = 4°C to 25°C, specimens are stable up to 72 hours
Fixed cell pellets are stable for years when stored at -28°C to 15°C
Storage & Handling

4°C to 25°C during transit, but specimens may be transported on refrigerated gel packs. Do not allow the gel pack to come in contact with the specimen. Do not freeze. Extreme temperatures should be avoided.

Causes for Rejection

Clotted specimen; Specimen exposed to extreme temperature; Anticoagulant toxic to cells; Insufficient number of cells; Improper fixative

Reference Range

See report

It is recommended that all FISH studies be done in conjunction with routine cytogenetic studies. If the FISH result is normal, a chromosome analysis allows identification of more complex abnormalities.


Williams syndrome is a rare genetic disorder found in approximately 1 in 7,500-20,000 people. A deletion on chromosome 7 is the cause for the disorder. This region includes several genes that most likely contribute to the characteristic features. Usually this disorder is seen as a random event and not inherited.


Elçioglu N et al. (1998). FISH analysis in patients with clinical diagnosis of Williams syndrome. Acta Paediatr. 87(1):48-53.