Use of test
Deletion of the SHOX gene can cause short stature and bone malformations. There are usually two copies of the SHOX gene on the X and Y Chromosomes (one copy on each). The loss of one copy results in a less severe disorder (Leri-Weill dyschondrosteosis) than loss of both copies (Langer mesomelic dysplasia). 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 which can cause the syndrome. Microarray testing can pick up smaller deletions within the SHOX 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 within the SHOX gene.
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.
15 business days for karyotype and FISH study; 3 business days for FISH alone.
This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost.
The Medicare details, including descriptor and schedule fee, are listed under MBS item 73291.