1. Care & Services
  2. Prenatal Diagnosis
  3. Carrier Testing
  4. Spinal Muscular Atrophy

Spinal Muscular Atrophy

Spinal Muscular Atrophy Carrier Screening


Spinal Muscular Atrophy (SMA) is a rare genetic disease that affects the motor nerve cells in the spinal cord and is the leading genetic cause of infant mortality. It is caused by an inherited faulty SMN1 gene. The SMN1 gene helps provide instructions to cells on how to produce the SMN (survival motor neuron) protein. If there isn’t enough correct SMN protein produced, it leads to degeneration of motor neurons. This creates problems with a person’s physical strength, often taking away the ability to walk, eat or even breathe. In the severe form, infants typically die by age 2. It’s impossible to restore already damaged neurons in a patient and therefore early diagnosis is essential. Gene therapy can help slow or stop the effects of the disease, greatly increasing the quality of life for the child as they grow older.

ACOG and ACMG have been recommending routine screening for SMA for some time now, but some patients decline the test because they would not consider termination. Neonatal gene therapy is a gamechanger—testing is now key in order to make sure that the newborn with SMA is identified and treated promptly after delivery.

There are currently two FDA approved gene therapies for SMA:

1. Zolgensma (AVXS-101)
The FDA approved Zolgensma (also known as AVXS-101), a gene therapy developed by AveXis (a gene therapy company owned by Novartis) for clinical use in the United States on children under two years of age with all types of SMA. Treated patients were able to breathe better, feed themselves, and sit unassisted. Patients must be treated before symptoms appear as the nerve degeneration is not reversible.

2. Spinraza (Nusinersen)
Spinraza helps increase the production of the SMN protein by using a backup gene called SMN2. With Spinraza’s help, enough SMN protein is produced.

Spinal Muscular Atrophy screening is NOT currently screened for in newborns but will be added to the routine Newborn screening in California sometime in 2020.

Prenatal carrier screening is available and should be offered to all pregnant patients regardless of ethnicity. About 1 in 50 women are carriers and about 1 in 10,000 children are born with SMA.


  1. Committee Opinion No. 690 Summary: Carrier Screening in the Age of Genomic Medicine. Obstet Gynecol. March 2017. doi: 10.1097/AOG.0000000000001947
  2. Committee Opinion No. 691: Carrier Screening for Genetic Conditions. Obstet Gynecol. March 2017. doi: 10.1097/AOG.0000000000001952
  3. https://www.fda.gov/news-events/press-announcements/fda-approves-innovative-gene-therapy-treat-pediatric-patients-spinal-muscular-atrophy-rare-disease