Spinal Muscular Atrophy (SMN1 gene) – Carrier Screening
Also known as: SMN1« Back to test list
Mutations in the SMN1 gene cause Spinal Muscular Atrophy (SMA), a disorder characterised by progressive symmetric muscle weakness that can be complicated by other features including joint contractures, scoliosis, growth failure and restrictive lung disease. Inheritance of SMA is autosomal recessive. About 1 in 40 people are SMA carriers, but carrier risk does vary by ethnic group.
This test detects deletions of the SMN1 gene which cause >95% of cases of SMA.
Carrier risk will depend on a patient’s family history and test results for other family members, however generally speaking test results are interpreted in the following way:
|1 copy of the SMN1 gene detected||Patient is a carrier of SMA|
|2 copies of the SMN1 gene detected||Patient is unlikely to be a carrier of SMA, but the possibility cannot be excluded|
This is an assay for heritable mutations. It may raise issues of ethics or consent that are different from most other investigations ordered in the routine care of a patient, and referral to a genetic counselling service may be appropriate.
Copy number analysis of the SMN1 gene by MLPA.
This test can be requested by any medical practitioner.
4 mL blood in EDTA (separate tube required). 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.
Please note whether or not the patient has a family history of SMA on the referral form. If there is a family history of SMA, please provide as much information as possible about the family pedigree and any previous testing that has been performed for other family members.