Spinal muscular atrophy testing

Last updated: Wednesday, 11, March, 2009

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Item Process
Specimen

10-20 mL blood in EDTA tube.

Method

PCR-based analysis to detect the presence of a deletion in the SMN (survival motor neurone) gene.

Application

Used in conjunction with muscle biopsy in the diagnosis of severe or intermediate spinal muscular atrophy. Not useful for identifying carriers.

Limited application in evaluation of older children or adults with recessive spinal muscular atrophy.

Not indicated in autosomal dominant spinal muscular atrophy.

Prenatal diagnosis for severe and intermediate forms of spinal muscular atrophy is available.

Interpretation

Approximately 90% of children with severe or intermediate forms of spinal muscular atrophy have deletions in both copies of this gene.

The identification of a deletion in both copies of the SMN gene in a symptomatic person is diagnostic of spinal muscular atrophy.

These methods do not detect all possible mutations.

The lack of deletions does not necessarily exclude the diagnosis. Family studies may allow prenatal diagnosis.

ReferenceLewin B. Cell 1995; 80: 1-5.