Continuum Audio Facioscapulohumeral Muscular Dystrophy With Dr. Renatta Knox
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common forms of muscular dystrophy, affecting individuals across the lifespan with variable severity. Advances in genetic understanding and therapeutic development have led to an era of promising disease-modifying strategies.
In this episode, Katie Grouse, MD FAAN, speaks with Renatta N. Knox, MD, PhD, author of the article “Facioscapulohumeral Muscular Dystrophy” in the Continuum® October 2025 Muscle and Neuromuscular Junction Disorders issue.
Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.
Dr. Knox is an assistant professor of neurology in the Division of Pediatric Neurology and Neuromuscular Section at Washington University School of Medicine in St. Louis, Missouri.
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Read the article: Facioscapulohumeral Muscular Dystrophy
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Full episode transcript available here
Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast.
Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Renatta Knox about her article on fascioscapulohumeral muscular dystrophy, which appears in the October 2025 Continuum issue on muscle and neuromuscular junction disorders. Welcome to the podcast, and please introduce yourself to our audience.
Dr Knox: Hi Katie, thank you so much for the invitation for the audio interview. I'm looking forward to our conversation. As she mentioned, my name is Renata Knox. It's a pleasure to be here today.
Dr Grouse: I'd like to start by asking, what is the key message that you hope your readers will take from your article?
Dr Knox: I would say two things. The first is an appreciation and understanding of the unique genetic mechanism that leads to FSHD. And the second is the really exciting therapy landscape that we find ourselves in. So, we're hopeful that there will actually be disease-modifying therapies for FSHD soon.
Dr Grouse: We're really looking forward to learning more about that. Now, before we get to that piece, could you just remind us of the clinical manifestations and features that are specific to FSHD?
Dr Knox: So, one of the most unique things about FSHD that we see clinically is the pattern of weakness. So, one of the first features is that it's asymmetric. And then there are certain muscle groups that typically are affected, and that's partly where the name comes from. So, we see effects in the face, the limbs, the trunk; and so, those are some of the unique features that we see clinically.
Dr Grouse: I'd love it if you could walk us through how you approach diagnosing a patient who presents with proximal weakness where FSHD is in your differential.
Dr Knox: Yeah, it's a really great question. So, I would say it depends. So, I actually focus on FSHD in my clinical practice. So, many times patients are referred to me because there's a very high suspicion or there's a known family history of FSHD. So, that's one category of cases. I would say the other category of case is where it's, as you said, maybe more proximal weakness more broadly. Someone that’s before me who has a known family history, they really have some of the characteristic physical features---which I'm pretty attuned to, as this is, you know, part of my subspecialty---I'll actually go directly to FSHD genetic testing. And that is one of the unique features of this disease, that the next-generation sequencing panels that are typically used for some of our other muscle diseases, FSHD is not captured on those. So, we actually have to send targeted testing for FSHD to diagnose it. So, that is one category where, again, I have a very high suspicion either based on their clinical presentation and/or a known family history, then I will actually go directly to FSHD-targeted genetic testing. In the second case, where it is one of the conditions that I'm considering among others, I will do more broad testing. So, I will get a CK level to see if there's evidence of muscle breakdown. I'll likely also do one of the next-generation sequencing panels that we have access to, which will allow us to identify, potentially, one to two hundred potential muscle diseases. And then again, if FSHD is higher on my differential in that second group of patients, then I will also send targeted FSHD-specific testing.
Dr Grouse: That's really helpful. And I'm wondering if you have any thoughts about common pitfalls that you've seen when providers are trying to work this up?
Dr Knox: I don't know if I would say pitfalls. I think I would acknowledge that it's challenging. My subspecialty training in neuromuscular medicine and also gene therapy. And so FSHD is pretty high on my radar. But I would say in neurology in general---and then, you know, the general medical population---,it really isn't something that many people are seeing. So, I would say what patients will communicate to us sometimes is some frustration that maybe it took time to make the diagnosis, but I just have a deep understanding that it's not something that is on many people's radars. And I think, again, it's tricky because it's not picked up on these next-generation sequencing panels, which many of us can send pretty easily. It will be missed. And I will say the biggest pitfall is, again, if you're not thinking about it and you don't send that testing, you actually- it's very difficult to diagnose it.
Dr Grouse: Thank you so much for highlighting that. I think there are many people who are not aware that those different panels really aren't picking that up and that they have to test specifically. So, I think that's a great thing for all of us to keep in mind. Are there any tips or tricks to the diagnosis, other than the genetic issues that you mentioned, that sometimes can really bring this diagnosis to the forefront?
Dr Knox: I think things that really tip me off to having a higher suspicion for FSHD is facial weakness that we can detect on our exam. Scapular winging---again, there's a small subset of disorders which can impact that. Someone who's presenting with foot drop, you know, with facial weakness, I think definitely about FSHD more. Also, clinically, kind of the presentation or things that they're beginning to have difficulty with is a tip-off. So, if someone is an athlete, like, they're a volleyball player or basketball player and they say, oh, I'm having difficulties, you know, with movements that require them to elevate their arm, which can be a sign of the shoulder weakness that we classically see. Or someone who says, oh, I'm having a harder time shampooing my hair or combing my hair. So those can be tip-offs again, which are basically referencing the type of weakness that they have. Another feature of FSHD which isn't necessarily as broadly appreciated is that pain and fatigue are very common. So, if someone is coming in and saying, actually, I also have a significant amount of fatigue as well or a lot of pain, that's something that can tip me off to it. Hearing loss is something that we can also see in up to 20% of patients with FSHD. So, if they are having those symptoms or saying they're ringing in their ears, these are some things that will make me begin to think about it more.
Dr Grouse: Oh, really helpful. I also found it really fascinating reading some of the very FSHD-specific clinical signs, some interesting- some diagrams and pictures as well, that are very specific to the pattern of weakness that develops in FSHD. So, I encourage our listeners to check that out. But are there any highlights from those little clinical pearls that you'd like to point out?
Dr Knox: I think the poly-hill sign---so, these are these literal hills that we can see in the shoulders of patients with FSHD---is pretty classic. Popeye arms, which is this older term that we still use that has to do with which muscle groups are preserved versus those that have atrophy. So that's a common feature. And then I would say, really, the asymmetry is something that is a unique feature in FSHD. And again, we did our best to provide good representative images. So again, as you mentioned, Katie, I would really encourage people to look at those images and then think about cases that they may have seen and how similar they are so they can begin to recognize those signs as well.
Dr Grouse: Now going back to the genetic topic, the complex genetic underpinnings of FSHD are really well-explained in your article; and again, worth taking a look at to remind ourselves of everything that's of that pathology. Now, I was wondering though, if you could give us a brief overview of how we should approach genetic testing in a suspected case of FSHD? You mentioned some specific panels, but it does sound like there's some more complexity to it as well.
Dr Knox: Yes, and I'll just kind of briefly explain that complexity. Part of the thing that we're detecting in the genetic testing is the repeat number. And so, we're actually looking for a contraction in a repeat number. So, not an expansion, which were typical for some of the diseases that we think about, the trinucleotide repeat disorders. And this is why it’s not captured in the next-generation sequencing panels, because they do not currently have the ability to do that. And so, again, what the type of testing that I do really depends on my suspicion. So again, if my suspicion is very high for FSHD---they have a family history, they have the classic features---then I will actually go directly to an FSHD-specific testing, which is available from various sources. If, again, it's among different things that I'm thinking about, I will get a CK lab. I typically will also send a next-generation sequencing panel specific for muscle diseases, perhaps muscular dystrophy; again, depending on what I'm thinking about. And then I will also send in a specific FSHD genetic test as well. People are beginning to use whole-genome sequencing, which is capturing some of our true nucleotide repeat disorders and becoming more comprehensive. So, my hope is that as that becomes more standard of care---like, whole-exome sequencing can be gotten pretty routinely now---that it may be easier for us to make some of these diagnoses.
Dr Grouse: Well, that's really helpful, and thanks for that overview. Now another thing that you mentioned that I thought was really interesting in your article was that patients with, you know, history of FSHD, perhaps in the family, who are pregnant and want to screen for this disease would not be able to use sort of the more common screening tests like cell-free DNA testing and may have to go to other means to do that. What is generally their route to this type of testing?
Dr Knox: Yeah, great question, and really important question for family planning purposes, and it definitely comes up in clinical practice. And so again, because of the unique genetics of FSHD, you actually have to do invasive genetic testing currently to be able to test it. And so that's, you know, amnio or chorio, and then send it to a lab that can perform, again, FSHD-specific testing on the samples that are presented. And there are obviously labs that are capable of doing that and centers that are capable of doing that, but it is not picked up on the cell-free DNA panels that are being very routinely used. You or your provider has to be thinking about it to send that specific testing, similar to our patients that come into clinic and have not yet been diagnosed.
Dr Grouse: Once you have the diagnosis, what are our options for therapy? I think it sounds like at this current time, it looks to be mostly supportive. What are some of the supportive care options we should keep in mind?
Dr Knox: Yes, so that is definitely accurate. Care today is supportive, but again, we're very excited about the clinical trial and therapy landscape for FSHD. So, I work very closely with my physical therapy colleagues that are in clinic with me. So, we work very closely with physical and occupational therapists to help with supportive measures, adaptive measures, doing assessments, helping our patients to be able to move and exercise safely and effectively. As I mentioned, pain is very common in FSHD and so we can treat that with medications. The most common medication that we use to treat for pain in FSHD are NSAIDs. And then other than that it's really, you know, supportive measures. Do they need to see other subspecialists? There are some surgical options. Those are used very rarely to help with some of the scapular weakness, but typically it's physical therapy, occupational therapy, supportive devices. We treat the pain as we're able to, and then we work with other subspecialists to screen, monitor and support our patients to the best of our ability.
Dr Grouse: Well, without further ado, I'd love to hear more about what's coming down the pipeline in clinical trials. What can we look forward to seeing, hopefully, in future years to treat these patients?
Dr Knox: Yes. And so, this is actually what got me interested in the neuromuscle space in general is that, because we now for many years have known the genetic cause of many of these disorders as well as some of the underlying mechanisms, we can actually use advances in therapeutics to do what we call targeted therapies. So, rather than treating symptoms or indirect methods or doing kind of broad drug screens---which, again, still do take place and still do have their place---we actually can target mechanisms directly. And so, we know that the underlying biology of FSHD is due to this protein called DUX4 being expressed when it should not be. So, it's what we call a toxic gain of function. And so, the targeted way to address this is to suppress DUX4 expression. And so, kind of broadly speaking, what we're really excited about are a couple of products that are currently in clinical trials right now that actually caused DUX4 suppression to be suppressed. And again, these are targeted pathways. And so, again, the hope is that by doing that, we can hopefully slow the progression of the disease, potentially stop progression of the disease, and potentially reverse. Again, we don't know if that might be possible, but that is one of the hopes.
Dr Grouse: Well, that's really exciting, and I know we're all looking forward to more coming down the pipeline soon, and hopefully more things that can really offer some exciting treatments for our patients with this condition. Now, a little more deep-dive into our patients who are diagnosed. You've reviewed some of the treatments currently available and hopefully may someday soon be available. Are there other things that we should be keeping in mind in this population? For instance, screenings that we should be doing for other extramuscular manifestations that we need to be thinking about?
Dr Knox: I will answer that question two ways. I think something that's very important to acknowledge is the impact that these diagnoses and these conditions have on our patient practically, psychologically. One of the other unique features of FSHD is, it's autosomal-dominant. So, if it is in a family, you can have many family members who are affected, but the variability is very high. And so, you can have in the same family someone who is wheelchair-dependent, and someone else in the family with the same underlying genetics who has no signs or symptoms or is very mildly affected. And that is something that is definitely challenging for our families and patients to navigate if they're very different than their family members with the same condition. And just navigating the world with a condition that, you know, can be physically debilitating and cause changes to what they're able to do or not able to do, progression is something that's very difficult to handle. So, I think that's one set of things. And we try our best, you know, with my team and my other colleagues in the space, to support our families and patients in the best way that we can.
Secondly, there is very important screening that needs to be done for this condition. So, one of the things- and the current guidelines which are actually being updated, the last update was in 2015 is all patients that undergo pulmonary function testing or PFTs. And so that's something we do at baseline and we do at least annually in my practice. Young kids who are presenting very early or patients with certain genetics that we know are more predisposed to extra muscular manifestations, we recommend screening for hearing, which is one of the manifestations, and ophthalmologic exam to look for retinovascular changes, which is one of the manifestations as well. Those are the more common ones that are typically done. There's also some evidence in pediatric patients with very severe manifestations that there may be some cognitive impacts, learning impacts. And so, that is something we're also thinking about screening and supporting our patients in that way. And again, we typically work with these patients in a multidisciplinary team depending on what manifestations and the degrees to which they're impacted by the disorder.
Dr Grouse: Thank you so much for that answer. I think a lot of us forget sometimes when we get really focused on what can we do now, that we forget to kind of stop and reflect on sort of the more holistic approach. How is this affecting the patient? How is this affecting the patient's family dynamic, and what other ways are they going through life with this condition that we need to be thinking about? So, I appreciate you bringing that up. I wanted to ask, sort of based on what you're talking about and what you mentioned already, you happened to mention that what initially drew you that to this work was your interest in some of the really exciting breakthroughs in the field. Well, was there anything else that drew you to, specifically, congenital neuromuscular diseases, and FSHD in particular?
Dr Knox: I'm a physician scientist by training, and so I would describe myself also as a molecular biologist. So, I love getting into the nitty gritties of disease mechanisms, what genes are doing in bodies, how they function. And so, as I mentioned earlier, in the neuromuscle space, we've known for many years the genetic cause of many of these disorders and have done great, you know, mechanistic work to kind of define why we see the disease. And then now we're at this intersection of that knowledge marrying with these really novel therapeutic approaches, gene therapy approaches, being able to intersect and then in very creative ways actually target diseases very directly. And so, I would say it really is the combination of those two things. FSHD has a really fascinating unique biology, which again, we encourage everyone to read about more in the article. That really drew me to it. I'm very interested in gene regulation, transcription. This is one of the underlying mechanisms that is gone awry in the disorder, and then that being married to advances in therapeutics. So, you could wed those two pieces of information and actually meaningfully impact patient 's lives.
And again, that's the real privilege and honor to witness is how these therapies can transform lives. And I saw it happened with this one case for this one disorder when I was a resident where there was no treatment. Young children, unfortunately, would not survive the disease. And then I saw the therapy come be in development and literally change the trajectory. And this is what we're very hopeful for in the FSHD space, that wedding, this wonderful basic science research, translational research, companies working together to develop these therapies that can transform lives. It is just so beautiful to witness and see, and it's something that I get to do. You know, it's a part of my job, so it's a real privilege.
Dr Grouse: Well, I have to say, it's really inspiring hearing you talk about it. And I imagine that many neurologists-in-training who are listening to this may be inspired as well and may be convinced to go into this field for that very reason. So, thank you so much for sharing all of this information with us today. I learned a lot, and I think all of our listeners have too.
Dr Knox: Thank you. It's really been a pleasure.
Dr Grouse: Again, today I've been interviewing Dr Renatta Knox about her article on fascioscapulohumeral muscular dystrophy, which appears in the October 2025 Continuum issue on muscle and neuromuscular junction disorders. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining today.
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