KERA’s Sam Baker talks with Dr. Angela Mix, a pediatrician at Texas Health Plano, about spinal muscular atrophy and the importance of adding it to the newborn screening panel.
INTERVIEW HIGHLIGHTS:
What happens is you have a loss of your spinal cord neurons; it's especially affecting your lower brain stem. And often, as it progresses in a baby, you're going to see that it affects the lower extremities more than the upper extremities. And then you actually have muscle weakness or atrophy and muscle wasting.
There's going to be a defect in a certain gene called the SMN-1 gene. And when you have the defect in that gene, you lose motor neurons that basically tell the muscles to help you walk, help you sit, help all of your tone.
In severe cases, you can't sit, you can't lift your head. You can't swallow. You can't walk.
- There's a type one that's going to present at less than six months of age. Or if you didn't have a newborn screen, those babies might look completely normal and healthy at birth, but they will progressively deteriorate.
- There's a type two, one that's a little bit more slowly progressive, but those kids develop scoliosis and contractures because they don't have the muscle support.
- And then there's one that presents a little later where they seem to be walking OK. Or they're maybe going to be a late walker. And they kind of present with limb weakness and that type of SMA can mimic other muscular disorders.
A baby that is born with SMA has to receive a missing or a faulty SMN-1 gene copy from both parents.
Both parents may be carriers, but that means they will have a 25% or 1 in 4 chance that their child will have SMA. It's rare, but still relatively common, because it's about 1ne in 8,000 to 11,000, depending on what you read.
With the addition of SMA, there are 31 core conditions that are tested. Also, 24 secondary conditions.
They're sometimes very difficult for a pediatrician to diagnose early. You have to put the baby through a lot of tests if you don't know what's going on. The newborn screening program is important because if you can identify some of these conditions early, you can begin treatment early and you can help the parents know what to expect, and they can be mentally prepared, and potentially they're not as afraid.
In the worst case, the little ones with the severe disease, 68% don't make it before the age of 2. 82% don't make it to the age of 4 in the most severe case. Those numbers may change now with early identification and treatment.
Types two and three may have to be treated for scoliosis or muscle contractures, or maybe they’ll need assisted devices like a wheelchair or a walker or something like that. But with treatment, I think the prognosis is much better.
RESOURCES:
SMA Foundation (https://smafoundation.org/about-sma/)
Carrier Screening for Spinal Muscular Atrophy (SMA)
Interview highlights were lightly edited for clarity.
Got a tip? Email Sam Baker at sbaker@kera.org. You can follow Sam on Twitter @srbkera.
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