There are four primary types of spinal muscular atrophy (SMA), with numerous variations. With so many conditions classified under the general SMA heading, sorting the facts from the myths can be challenging.
Below are straight answers to some of the most common misperceptions about SMA, from diagnosis and genetic carriers to life expectancy and quality of life.
Myth: An SMA diagnosis means a shortened lifespan, period
Fact: Fortunately, this isn’t the case. Infants with type 0 SMA typically don’t survive past 6 months of age. Children with severe type 1 SMA often don’t survive to adulthood, though there are many factors that can prolong and improve the quality of life in these children. But children with types 2 and 3 generally live into adulthood. With appropriate therapies, including physical and respiratory treatments, along with nutritional support, many live full lives. Symptom severity also has an impact. But a diagnosis alone isn’t enough to determine longevity.
Myth: Children with SMA can’t thrive in public education settings
Fact: SMA doesn’t affect a person’s mental or intellectual capacity in any way. Even if a child is wheelchair-dependent by the time they reach school age, public schools in the United States are required to have programs in place to accommodate special physical needs. Public schools must also facilitate specialized learning programs such as an Individualized Education Program (IEP) or a “504 Plan,” a name which comes from section 504 of the Rehabilitation Act and the Americans with Disabilities Act. In addition, many adaptive devices are available for children who want to participate in sports. For many kids with SMA, a more “normal” school experience is within reach.
Myth: SMA can only occur if both parents are carriers
Fact: SMA is a recessive disease, so typically a child will only have SMA if both parents pass on the SMN1 mutation. There are, however, a couple of notable exceptions.
According to the nonprofit advocacy group Cure SMA, when two parents are carriers:
- Their child has a 25 percent chance of being unaffected.
- Their child has a 50 percent chance of becoming a carrier.
- Their child has a 25 percent chance that they will have SMA.
If only one parent is a carrier, the child is usually not at risk for SMA, though they do have a 50 percent risk of being a carrier. However, in very rare cases, mutations in the SMN1 gene can occur during egg or sperm production. As a result, only one parent will be a carrier of the SMN1 mutation. In addition, a small percentage of carriers have a mutation that can’t be identified through current testing. In this case, it will appear as though the disease has been caused by a single carrier.
Myth: 95 percent of all SMA carriers can be identified with a simple blood draw
Fact: According to one study, five of the six ethnic groups identified for testing in the United States have detection rates over 90 percent, including Caucasian, Ashkenazi Jews, Hispanics, Asians, and Asian Indians. Among African-Americans, the test is only about 70 percent effective. This is believed to be due to a generally increased likelihood of undetectable mutations in this population.
Myth: If one or both parents carry the SMN1 mutation, there is no guarantee that a child won’t be a carrier or affected directly by SMA
Fact: In addition to prenatal tests, parents opting for implantation can screen for genetic diagnoses beforehand. This is known as pre-implantation genetic diagnosis (PGD), and it allows only healthy embryos to be implanted. Of course, implantation and prenatal testing are all highly personal decisions, and there is no single right answer. Prospective parents must make these choices for themselves.
With a diagnosis of SMA, a person’s life is permanently altered. Even in the mildest cases, physical difficulties that increase over time are certain. But equipped with good information and a commitment to striving for their best life possible, a person with SMA doesn’t have to live without dreams and achievements. Many with SMA lead full lives, graduate college, and make meaningful contributions to the world. Knowing the facts is the best place to start the journey.