Q: Could I or my spouse be a carrier of SMA and not know it?
A: Yes. Carriers do not have SMA nor any symptoms of the disease. Moreover, they may have no family history of the disease and may have healthy children. The only way to know whether you are a carrier of SMA is to be tested with a simple blood test, ideally before conception or in early pregnancy.
Q: If my spouse and I test negative for being SMA carriers, does that mean our baby will not have SMA?
A: No, although it does mean that your risks are greatly reduced. While it has a very high detection rate compared to many other genetic tests, SMA carrier testing cannot currently detect all carriers, specifically those with rare mutations. Generally speaking, SMA carrier testing detects about 90% of carriers (this increases to about 92-94% with Athena Diagnostics' "SMA Plus" test, which will be available in early 2010).
Q: What groups are most affected by SMA?
A: Unlike some other genetic diseases that affect only certain populations, such as Tay-Sachs disease, SMA affects all populations worldwide equally, regardless of race or ethnicity. This is one of the reasons the American College of Medical Genetics recently recommended that all couples be tested for SMA before conception or early in pregnancy.
Q: If I'm an SMA carrier but my spouse isn't, does that mean our child could be born with SMA?
A: In most cases, No. SMA is an autosomal recessive genetic disorder, which means that both parents must have the mutation responsible for the disorder to have a child with the disease. And even when both parents are SMA carriers, that does not mean that all (or even any) of their children will have SMA, although there is a significantly increased risk. Specifically, there is a 25% chance with each pregnancy that the child of parents who are both SMA carriers will have SMA. Conversely, that also means that there is a 75% chance with each pregnancy that the child will not have SMA.
We have to remember that while the SMA Carrier test is a very reliable test, it will only detect 93% of carriers due to the incidence of the 2+0 carrier rate (3%), the de novo rate (2%) and point mutations (2%-4%) in the general population and that the SMA Carrier test will not detect.
Q: Is there a cure for SMA?
A: Unfortunately, at this time the answer is no. However, research aimed at finding a treatment or cure for SMA is moving rapidly forward. Much of this research is focused on SMN2, a gene that partially compensates for the function of the gene (SMN1) that, when mutated (abnormal), is the cause of most cases of SMA.
Q: If we have a baby with SMA, what is his or her prognosis?
A: There are many factors that influence a child's prognosis, including the type of SMA he or she has. Babies with type I SMA, which is the most common and severe form of the disease, have the poorest prognosis, often dying before they reach age two. By contrast, children with type III SMA, the mildest form, will face challenges, but can learn to walk unaided and live a normal lifespan. The type of SMA is influenced by the number of copies of a back-up gene, called SMN2, a child with SMA has. This information is exclusively provided by Athena Diagnostics' SMA tests.