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Diseases

Genetic and Rare Diseases Information Center (GARD)

Spinal muscular atrophy 1


Other Names for this Disease
  • Infantile spinal muscular atrophy
  • Muscular atrophy, infantile
  • Proximal spinal muscular atrophy type 1
  • Proximal spinal muscular atrophy, type 1
  • SMA, infantile acute form
Related Diseases
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Tests & Diagnosis

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Is genetic testing available for spinal muscular atrophy 1?

Genetic testing for spinal muscular atrophy 1 (SMA1) is available. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible, if the disease-causing mutations in the family have been identified. SMA1 is caused by mutations in the SMN1 gene, and extra copies of the SMN2 gene affect the severity of the condition.[1]

In some cases, interpreting results of carrier testing for SMA is difficult. Approximately 6% of parents of a child with SMA due to deletions in each copy of the gene have normal results of SMN1 dosage testing (carrier testing) for one of two reasons. Most people have one copy of SMN1 on each chromosome. However, about 4% of carriers have two copies of SMN1 on a single chromosome and a deletion on the other chromosome. These carriers with two copies of SMN1 on one chromosome are misdiagnosed as non-carriers by the SMN1 dosage test (they have a false negative test result). The second reason is that a new (de novo) deletion on one copy of the SMN1 gene occurs in 2% of people with SMA; in these cases, only one parent is a carrier.[1]

The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The Genetic Testing Registry (GTR) is a centralized online resource for information about genetic tests. The intended audience for the GTR is health care providers and researchers. The genetics of SMA1 is complex. People with specific questions about genetic risks and genetic testing for themselves or family members should speak with a genetics professional.
Last updated: 1/21/2015

References
  1. Thomas W Prior and Barry S Russman. Spinal Muscular Atrophy. GeneReviews. November 14, 2013; http://www.ncbi.nlm.nih.gov/books/NBK1352/.


Testing

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
Other Names for this Disease
  • Infantile spinal muscular atrophy
  • Muscular atrophy, infantile
  • Proximal spinal muscular atrophy type 1
  • Proximal spinal muscular atrophy, type 1
  • SMA, infantile acute form
Related Diseases
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.