Experts Discuss Symptoms, Types, and Treatments of SMA

A recent Peer Exchange series from The American Journal of Managed Care^® brought together a panel of experts to discuss spinal muscular atrophy (SMA), including its clinical presentation, diagnosis of its various types, and the potential of new disease-modifying treatments. The panel was moderated by Peter L. Salgo, MD.

SMA is not a common disease, and Salgo admitted he was unaware of it until he began preparing to moderate the series, but it is “actually the most common genetic cause of infant death,” according to John Brandsema, MD.¹ This neurodegenerative disorder most commonly presents in infants with symptoms of limb weakness. In the most severe form of the disease, SMA type 1, which has the earliest onset, symptoms include impaired respiratory function.

“The most common thing would be in an infant, hypotonia and a little bit of floppiness, which can be part of normal spectrum of development in some kids. Most primary specialists might think of something like instituting some physical therapy for a couple of months and seeing whether that helps the patient,” Brandsema explained. “But in SMA type 1, that is an eternity because they’re going to get worse during that time and start to show problems with their breathing and their feeding.”¹

To confirm suspected SMA, clinicians perform genetic testing to search for double deletion of the SMN1 gene, which causes the SMN protein deficiency that leads to the symptoms of motor neuron loss and weakness.²

The type of diagnostic scale used to assess the severity of SMA depends on a patient’s age, Brandsema said.² Young infants with type 1 SMA will often undergo the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders and the Hammersmith Infant Neurological Exam, whereas slightly older patients with type 2 or type 3 disease would be measured with the Hammersmith Functional Motor Scale.

“You’re really trying to find the right test that’s going to measure the patient’s function in the moment and also how they’re changing—which, in the natural history, would be loss over time on these scales of points or function,” Brandsema said. “But with these new disease-modifying therapies, it may in fact be improvement.”²

The new targeted gene therapies that Brandsema referenced have produced significant therapeutic impact and changed the landscape of SMA treatment, but insurance coverage can determine patients’ access. Payers are not sure how long the benefits of treatment will last, which makes it difficult for them to determine the value of these treatments, according to Surya Singh, MD.

“People usually think about longevity in terms of the patient,” Singh explained. “But here, as we’re just about on the cusp of sort of viral delivered gene therapy…the question becomes, does this method for producing the protein that we want continue to work? Or does the body find some way to be able to decrease those levels? And what happens then? Does it require a boost?”³

Although these questions have yet to be answered, the panelists agreed that the therapeutic developments have given hope to families who previously had none.

“I’m excited, and I am proud to be in a profession that has done this for people and is continuing to do this for people—and that includes insurance,” Salgo concluded. “Everybody has got a piece of this, and it’s all going the right way.”⁴

References

1. Spinal muscular atrophy (SMA) and types of SMA. The American Journal of Managed Care® website. ajmc.com/peer-exchange/rare-neurological-diseases/spinal-muscular-atrophy-sma-and-types-of-sma. Published July 8, 2019. Accessed August 20, 2019.

2. Diagnostic tests and scales of SMA. The American Journal of Managed Care® website. ajmc.com/peer-exchange/rare-neurological-diseases/diagnostic-tests-and-scales-of-sma. Published July 22, 2019. Accessed August 20, 2019.

3. Payer perspective and value of treatment of SMA. The American Journal of Managed Care® website. ajmc.com/peer-exchange/rare-neurological-diseases/segment-title-payer-perspective-and-value-of-treatment-of-sma. Published August 12, 2019. Accessed August 20, 2019.

4. Risdiplam and final thoughts. The American Journal of Managed Care® website. ajmc.com/peer-exchange/rare-neurological-diseases/risdiplam-and-final-thoughts. Published August 19, 2019. Accessed August 20, 2019.