Case-Based Insights: Expert Perspectives on the Treatment of Adult-Onset SMA - Episode 3

A 38-Year-Old Female with Spinal Muscular Atrophy

James Wymer, MD, provides a case overview of a 38-year-old female diagnosed with spinal muscular atrophy.

James Wymer, MD: I want to discuss the case of a young woman who presented for evaluation. This is a 38-year-old woman who had been previously diagnosed with what was called muscular dystrophy. This occurred around age 9 because she was having some difficulty and muscle weakness. She said she started with the weakness, that it was primarily in her hips and her thighs. She couldn’t walk that far because she was getting significant muscle fatigue and having some difficulty breathing. She then saw her primary care physician, and they sent her to a neurologist. The neurologist did some examination and ordered some blood work. In the process, when they evaluated it, they had concerns for spinal muscular atrophy [SMA]. They sent off genetic testing and it showed an absence of SMA1 with a slightly elevated creatinine kinase, or CK. Because of that and because this patient is 38 years old, they were diagnosed with type 4 SMA. The neurologist discussed the treatment options, started the patient on risdiplam because they wanted to take a pill to treat this, and then referred the patient for OT [occupational therapy], PT [physical therapy], and a pulmonary evaluation.

This classic pattern that we’re seeing led to that muscular dystrophy diagnosis. A young girl at age 9 was having some difficulty running and was having some muscle weakness. And that’s the proximal weakness that we’ll see. As a neuromuscular specialist, we’ll see this in a lot of patients who are having some form of muscular dystrophy, and that’s why these questions were initially raised about that. But what complicates it is we had this difficulty breathing there was a lot of respiratory, there was a lot of different muscle. There was fatigue that was going on, and this pointed us again towards that muscular dystrophy but also more, could it be something else because the respiratory was a little bit more involved in it? When you examine somebody at this age in the differential, you start thinking about other processes. Muscular dystrophy is a muscle disease, which this could be, but in your lab work you can see there’s talk about a slightly elevated CK, but in muscular dystrophy it’s more dramatically elevated. That’s going to point you toward other causes, of which SMA becomes a real possibility. Spinal muscular atrophy is a disease of the motor neurons, not of the muscle. Initially looking at this, you think about this being not just a muscular dystrophy but something more than that. The SMA becomes in the differential, and that’s where that testing comes up. The thing about SMA is SMA is really a spectrum disease. You can have some of the SMAs that can be severe and can present at birth. Some can present in their adulthood. And those are more of the type 4s. This symptom starting around age 9 would be more suggestive of a type 3 SMA, but type 4 would certainly be 1 thing that could come up.

Transcript Edited for Clarity