NOTICE: We are continuing to provide all of our genetic testing during the COVID-19 pandemic, but the reporting times for some of our tests may be slower than usual. This delay could be due to three reasons:
laboratory resources being directed to testing for COVID-19
fewer interstate flights for shipping samples
a backlog of tests as restrictions on elective surgery and procedures are lifted
We apologise for any delay in reporting your genetic test result.
If you have any concerns about this, please speak with the doctor who ordered your genetic test.
Also known as: Sotos FISH, cerebral gigantism FISH, NSD1 FISH
Paediatric - Congenital disorder
Use of test
Deletion of the NSD1 gene on Chromosome 5 can cause a characteristic syndrome of abnormal neurodevelopment, malformations, and overgrowth (Sotos syndrome). This test provides diagnostic information.
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 does not exclude a clinical diagnosis as there are other mutations on Chromosome 5 which can cause the syndrome. Microarray testing can pick up smaller deletions within the Sotos gene.
These mutations are usually de novo and do not increase the risk of this disorder in siblings or other relatives. However a parent and other relatives may carry a balanced translocation involving this chromosome region and be at increased risk of having an affected child.
Fluorescent in situ hybridisation (FISH) analysis using probes located in the NSD1 gene on Chromosome 5.
Requesting the test
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 EDTA and 2-5 mL blood in lithium-heparin. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).
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 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.