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:
- 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)