What is the role of genetic testing in the workup of spinal muscular atrophy (SMA)?

Updated: May 29, 2019
  • Author: Jeffrey Rosenfeld, MD, PhD, FAAN; Chief Editor: Stephen L Nelson, Jr, MD, PhD, FAACPDM, FAAN, FAAP  more...
  • Print

Both prenatal and postnatal tests are now commercially available.

Homozygous SMN1 gene deletion is 95% sensitive and nearly 100% specific for the diagnosis of SMA. In patients with suspected disease and no gene deletion, SMN1 copy testing with sequencing of coding regions of SMN1 copy (if present) is suggested. [38]  Molecular testing for homozygous deletion or mutation of the SMN1 gene allows efficient and specific diagnosis. [39]

The 1992 ISMAC found that the accuracy of prenatal prediction by means of chorionic villi sampling and amniocentesis was 88-99%.

Caution should be exercised when prenatal prediction is done in the presence of atypical features (see SMA variants in Physical) because these clinical variations may represent other pathogenic processes.

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!