By Carol Guzman

August marks Spinal Muscular Atrophy (SMA) Awareness month, which aims to increase awareness and advocacy efforts for the rare genetic disorder. SMA affects the nerves in the spine that control the muscles for breathing, swallowing, and limb movement. The disorder causes these neurons to degrade, resulting in a child having weak muscles and loss of muscle control. SMA occurs in approximately 1 in 800 live births. The disorder is inherited in the autosomal recessive fashion, meaning if both parents are carriers for SMA, each of their children has a 25% likelihood of having SMA, a 50% chance of carrying the SMA-causing mutation without health effects, and a 25% chance of not carrying the mutation at all. SMA is one of the most common inherited causes of childhood mortality, second only to cystic fibrosis. Fortunately, screening and treatment options for this devastating disorder are available.

In 2017, The American College of Obstetricians and Gynecologists (ACOG) recommended that all women considering pregnancy or currently pregnant be offered screening for SMA, along with cystic fibrosis, and hemoglobin-related disease. While the three recommended diseases are Jewish genetic disorders because of their high carrier frequencies within the Jewish population, the diseases still have relatively high carrier frequencies in the general population. For SMA specifically, the carrier frequency in the Ashkenazi Jewish population is 1 in 62, while in the general population the carrier frequency is 1 in 49. 

There are various SMA types, each with its own characteristics and symptoms:

• Type I is the most severe form of SMA and can cause death from respiratory failure within 2 years.
• Type II is less severe; patients with this type of SMA can lived up to their mid-20s.
• Type III exhibits symptoms after 18 months
• Type IV shows symptoms in adulthood

There are now treatment options for SMA, which was once considered an incurable disease. However, the earlier an infant is diagnosed with SMA, the earlier they can receive treatment to prevent and delay motor neuron degeneration. Carrier screening before pregnancy allows partners to identify whether their future child will inherit an early onset recessive disorder. ACOG recommends that individuals of Ashkenazic ancestry should be screened for additional diseases, including Canavan disease, Familial Dysautonomia, and Tay-Sachs. However, there are many more diseases people of Ashkenazi descent, including those in an interfaith partnership, should consider being screened for even though they are less common in the global population.

Consider talking to your health care provider or a genetic counselor about carrier screening before family planning. In addition, join us on Oct. 6 for Decoding Genetic Tests for Parents to Be, a program that will focus on all the genetic tests offered pre and postnatally.

To learn more about the Sarnoff Center’s affordable, accessible carrier screening program or to speak with a genetic counselor, visit Jewishgenetics.org/cjg/get-screened or contact us at GeneticScreening@juf.org

Additional Resources: 

1. Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG) | Genetics in Medicine (nature.com)