Next Diagnostic Steps: Genetics First

Dystrophinopathies are heritable muscle disorders caused by pathogenic variants in the DMD gene, leading to progressive muscle breakdown, proximal weakness, cardiomyopathy, and respiratory failure. Diagnosis and management are evolving areas of neuromuscular neurology.

In this episode, Kait Nevel, MD, speaks with Divya Jayaraman, MD, PhD, an author of the article "Dystrophinopathies" in the Continuum® October 2025 Muscle and Neuromuscular Junction Disorders issue.

Dr. Nevel is a Continuum® Audio interviewer and a neurologist and neuro-oncologist at Indiana University School of Medicine in Indianapolis, Indiana.

Dr. Jayaraman is an assistant professor of neurology and pediatrics in the division of child neurology at the Columbia University Irving Medical Center in New York, New York.

Additional Resources

Read the article: Dystrophinopathies

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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 Nevel: Hello, this is Dr Kate Nevel. Today I'm interviewing Dr Divya Jayaraman about her article on dystrophinopathies, which she wrote with Dr Partha Ghosh. This article appears in the October 2025 Continuum issue on muscle and neuromuscular junction disorders. Divya, welcome to the podcast, and please introduce yourself to the audience.

Dr Jayaraman: Thank you so much, Dr Nevel. My name is Divya, and I am an assistant professor of Neurology and Pediatrics at Columbia University Irving Medical Center, and also an attending physician in the Pediatric Neuromuscular program there. In that capacity, I see patients with pediatric neuromuscular disorders and also some general pediatric neurology patients and also do research, primarily clinical research and clinical trials on pediatric neuromuscular disorders.

Dr Nevel: Wonderful. Thank you for sharing that background with us. To set us on the same page for our discussion, before we get into some more details of the article, perhaps, could you start with some definitions? What comprises the dystrophinopathies? What are some of the core features?

Dr Jayaraman: So, the dystrophinopathies, I like that term because it is a smaller subset from the muscular dystrophies. The dystrophinopathies are a spectrum of clinical phenotypes that are all associated with mutations in the DMD gene on chromosome X. So, that includes DMD---or, Duchenne muscular dystrophy---, Becker muscular dystrophy, intermediate muscular dystrophy (which falls in between the two), dilated cardiomyopathy, asymptomatic hyperCKemia, and manifesting female carriers. In terms of the core features of these conditions, so, there's some variability, weakness being prominent in Duchenne and also Becker. The asymptomatic hyperCKemia, on the other hand, may have minimal symptoms and might be found incidentally by just having a high CK on their labs. They all will have some degree of elevated CK. The dilated cardiomyopathy patients, and also the Becker patients to a lesser degree, will have cardiac involvement out of proportion to skeletal muscle involvement, and then the manifesting carriers likewise can have elevated CK and prominent cardiac involvement as well as some milder weakness.

Dr Nevel: Now that we have some definitions, for the practicing neurologists out there, what do you think is the most important takeaway from your article about the dystrophinopathies?

Dr Jayaraman: I like this question because it suggests that there's something that, really, any neurologist could do to help us pick up these patients sooner. And the big takeaway I want everyone to get from this is to check the CK, or creatine kinase, level. It's a simple, cheap, easy test that anyone can order, and it really helps us a lot in terms of setting the patient on the diagnostic odyssey. And in terms of whom you should be thinking about checking a CK in, obviously patients who present with some of the classic clinical features of Duchenne muscular dystrophy. This would include young boys who have toe walking, as they're presenting, sign; or motor delayed, delayed walking. They may have calf hypertrophy, which is what we say nowadays. You might have seen calf pseudohypertrophy in your neurology textbooks, but we just say calf hypertrophy now. Or patients can often have a Gowers sign or Gowers maneuver, which is named after a person called Gowers who described this phenomenon where the child will basically turn over and use their hands on the floor to stand up, usually with a wide-based gait, and then they'll sort of march their hands up their legs. That's the sort of classic Gowers maneuver. There are modified versions of that as well.

So, if anyone presents with this classic presentation, for sure the best first step is to check a CK. But I would also think about checking a CK for some atypical cases. For example, any boy with any kind of motor or speech delay for whom you might not necessarily be thinking about a muscle disorder, it's always good practice to check a CK. Even a boy with autism for whom you may not get a good clinical exam. This patient might present to a general pediatric neurology clinic. I always check a CK in those patients, and you'll pick up a lot of cases that way. For the adult folks in particular, the adult neurologist, a female patient could show up in your clinic with asymptomatic hyperCKemia. And I think it's an important differential to think about for them because this could have implications not just for their own cardiac risks, but also for their family planning.

Dr Nevel: So, tell us a little bit more about the timing of diagnosis. Biggest takeaway: check a CK if this is anywhere on your radar, even if somewhat of an atypical case. Why is it so important to get kiddos started on that diagnostic odyssey, as you called it, early?

Dr Jayaraman: This is especially important for kids because if they especially get a Duchenne muscular dystrophy diagnosis, you might be making them eligible for treatments that we've had for some time, and also treatments that were not available earlier that hinge on making that diagnosis. So, for example, people may be skeptical about steroids, but there's population data to suggest that initiation and implementation of steroids could delay the onset of loss of ambulation as much as three years. So, you don't want to deprive patients of the chance to get that. And then all the newer emerging therapies---which we'll be talking about later, I'm sure---require a Duchenne muscular dystrophy diagnosis. So, that's why it's so important to check a CK, have this on your radar, and then get them to a good specialist.

Dr Nevel: I know that you alluded already, or shared a few of the kind of exam paroles or findings among patients with dystrophinopathy. But could you share with us a little bit more how you approach these patients in the clinic who are presenting with muscle weakness, perhaps? And how do you approach this or think about this in terms of ways to potentially differentiate between a dystrophinopathy versus another cause of motor weakness or delay?

Dr Jayaraman: It's helpful to think through the neuraxis and what kinds of disorders can present along that neuraxis. A major differential that I'm always thinking about when I'm seeing a child with proximal weakness is spinal muscular atrophy, which is a genetic anterior horn cell disorder that can also present in this age group. And some of the key differences there would be things like reflexes. So, you should have dropped reflexes in spinal muscular atrophy. In DMD, surprisingly, they might have preserved Achilles reflexes even if their patellar reflexes are lost. It may only be much later that they go on to lose their Achilles reflex. So, if you can get an Achilles reflex, that's quite reassuring, and if you cannot, then you need to be thinking about spinal muscular atrophy. They can both have low muscle tone and can present quite similarly, including with proximal weakness, and can even have neck flexion weakness. So, this is an important distinction to make. The reason for that is, obviously there are treatments for both conditions, but for spinal muscular atrophy, timing is very, very important. Time is motor neurons, so the sooner you make that diagnosis the better.

Other considerations would be the congenital muscular dystrophies. So, for those that they tend to present a lot younger, like in infancy or very early on, and they can have much, much higher CKS in that age range than a comparable Duchenne or Becker muscular dystrophy patient. They can also have other involvement of the central nervous system that you wouldn't see in the dystrophinopathies, for example. My mnemonic for the congenital muscular dystrophies is muscle-eye-brain disease, which is one of the subtypes. So, you think about muscle involvement, eye involvement, and brain involvement. So, they need an ophthalmology valve. They can have brain malformations, which you typically don't see in the dystrophinopathies. I think those are some of the major considerations that I have. Obviously, it's always good to think about the rest of the neuraxis as well. Like, could this be a central nervous system process? Do they have upper motor neuron signs? But that's just using all of your exam tools as a neurologist.

Dr Nevel: Yeah, absolutely. So, let's say you have a patient in clinic and you suspect they may have a dystrophinopathy. What is your next diagnostic step after your exam? Maybe you have an elevated CK and you've met with the patient. What comes next?

Dr Jayaraman: Great question. So, after the CK, my next step is to go to genetics. And this is a bit of a change in practice over time. In the past we would go from the CK to the muscle biopsy before genetic testing was standard. And I think now, especially in kids, we want to try and spare them invasive procedures where possible. So, genetic testing would be the next step. There are a few no-charge, sponsored testing programs for the dystrophinopathies and also for some of the differential diagnosis that I mentioned. And I think we'll be including links to websites for all of these in the final version of the published article. So, those are a good starting point for a genetic workup. It's really important to know that, you know, deletions and duplications are a very common type of mutation in the DMD gene. And so, if you just do a very broad testing, like whole exome, you might miss some of those duplications and deletions. And it's important to include both checking for duplications and deletions, and also making sure that the DMD gene is sequenced. So always look at whatever genetic test you're ordering and making sure that it's actually going to do what you want it to do.

After genetics, I think that the sort of natural question is, what if things are not clear after the genetics for some reason? We still use biopsy in this day and age, but we save it for those cases where it's not entirely clear or maybe the phenotype is a little bit discordant from the genotype. So, for mutations that disrupt the reading frame, those tend to cause Duchenne muscular dystrophy, whereas mutations that preserve the reading frame tend to cause Becker muscular dystrophy. There are some important exceptions to this, which is where muscle biopsy can be especially helpful in sorting it out.

So, for example, there are some early mutations early in the DMD gene where, basically, they find an alternate start codon or an initiation codon to continue with transcription and translation. So, you end up forming a largely functional, somewhat truncated protein that gives you more of a milder Becker phenotype. On the other hand, you can have some non-frameshift or inframe mutations that preserve the reading frame, but because they disrupt a very key domain in the protein that's really crucial for its function, you can actually end up with a much more severe Duchennelike phenotype. So, for these sorts of cases, you might know a priori you're dealing with them, but might just be a child who is who you think has DMD has a mutation that's showed up on testing. There isn't enough in the literature to point you one way or another, but they look maybe a little milder than you would expect. That would be a good kid to do a biopsy in because there are treatment decisions that hinge on this. There are treatments that are only for Duchenne that someone with a milder phenotype would not be eligible for.

Dr Nevel: So, that kind of stepwise approach, but maybe not all kids need a muscle biopsy is what I'm hearing from you. If it's a mutation that's been well-described in the literature to be fitting with Duchenne, for example.

Dr Jayaraman: Absolutely.

Dr Nevel: So, after you confirm the diagnosis through genetic testing---and let's say, you know, whether or not you do a muscle biopsy or not, after you know the diagnosis is a dystrophinopathy---how do you counsel the families and your patients? What are the most important points to relay to families, especially in that initial phase where the diagnosis is being made?

Dr Jayaraman: This is a lot of what we do in pediatric neurology in general, right? So, I actually picked up this approach from the pediatric hematology oncology specialists at Boston Children's. They had this concept of a day-zero conversation, which is the day that you disclose the life-changing diagnosis or potentially, at some point, terminal diagnosis to a family. And some of the key components of that are a not beating around the bush, telling them what the diagnosis is, and then letting them have whatever emotional response they're going to have in the moment. And you may not get much further than that, but honestly, you want them to take away, this is what my child has. I did not do anything to cause this, nor could I have done anything to prevent this. Because often for these genetic conditions, there's a lot of guilt, a lot of parental guilt. So, you want to try and assuage that as much as possible. And then to know that they're not going to be alone on this journey; that, you know, they don't have to have it all figured out right then, but we can always come back and answer any questions they have. There's going to be a whole team of specialists. We're going to help the family and the kid manage this condition. Those are sort of my big takeaways that I want them to get.

Dr Nevel: Right. And that segues into my next question, which is, who is part of that team? I know that these teams that help take care of people with dystrophinopathies and other muscle disorders can be very large teams that span multiple specialists. Can you talk a little bit more about that for this group of patients?

Dr Jayaraman: Of course. So, the neuromuscular neurologist, really, our role is in coordinating the diagnosis, the initiation of any disease-specific treatments, and coordinating care with a whole group of specialists. So, we're sort of at the center of that, but everyone else is equally important. So, the other specialists include physical therapists; occupational therapists; rehab doctors or physiatrists; orthotists who help with all of the many braces and other devices that they might need, wheelchairs; pulmonology, of course, for managing the respiratory manifestations of this. It becomes increasingly important over time, and they are involved early on to help monitor for impending respiratory problems. Cardiac manifestations, this is huge and something that you should be thinking about even for your female carriers, the mother of the patient you're seeing in the clinic, or your patient who comes to adult clinic with asymptomatic hyperCKemia. if you end up making a diagnosis of DMD carrier for those patients, or if you make a Becker diagnosis, the cardiac surveillance is even more important because the cardiac involvement can be out of proportion to the skeletal muscle weakness. And of course, extremely important for the Duchenne patients as well.

Endocrinologists are hugely important because in the course of treating patients with steroids, we end up giving them a lot of iatrogenic endocrinologic complications. Like they might have delayed puberty, they might have loss of growth, of height; and of course metabolic syndrome. So, endocrinology is hugely important. They're also important in managing things like fracture prevention, osteoporosis, prescribing bisphosphonates if necessary. Nutrition and GI are also important, not just later on when they might need assistance to take in nutrition, whether that's through tube feeds, but also earlier on when we're trying to manage the weight. Orthopedics, of course, for the various orthopedic complications that patients develop. And then finally, a word must be said for social work and behavioral and mental health specialists, because a lot of this patient population has a lot of mental health challenges as well.

Dr Nevel: After you give the diagnosis, you've counseled the patient and families and you've had those kind of initial phase discussions, the day-zero discussion, when you start getting into discussions or thoughts about management, disease-specific medication. But what are the main categories of the treatment options, and maybe how do you kind of approach deciding between treatment options for your patients?

Dr Jayaraman: So, there are two broad categories that I like to think about. So, one is the oral corticosteroids and oral histone deacetylase, or HDAC inhibitors, which share the common characteristic that they are non-mutation specific. And within corticosteroids, patients now have a choice between just Prednisone or Prednisolone, or Deflazacort or Vermilion. The oral HDAC inhibitors are newly FDA-approved as a nonsteroidal therapy in addition to corticosteroids in DMD patients above six years of age. I would say we're in the early phase of adoption of this in clinical practice. And then the other big category of treatment options would be the genetic therapies as a broad bucket, and this would include gene therapy or gene replacement therapy, of which the most famous is the microdystrophin gene therapy that was FDA-approved first on an accelerated approval basis for ages four to eight, and then a full approval in that age group as well as an accelerated approval for all comers, essentially, with DMD. This is obviously controversial. Different centers approach this a bit differently. I think our practice at our site has been to focus on the ambulatory population, just thinking about risk versus benefit, because the risks are not insignificant. So really this is something that should be done by experienced sites that have the bandwidth and the wherewithal to counsel patients through all of this and to manage complications as they arise with regular monitoring.

And then another class that falls within this broader category would be the Exon-skipping therapies. So as the name suggests, they are oligonucleotides that cause an Exon to be skipped. The idea is, if there is a mutation in a particular Exon that causes a frame shift, and there's an adjacent Exon that you can force skipping of, then the resulting protein, when you splice the two ends together, will actually allow restoration of the reading frame. I think the picture I want to paint is that there's a wide range of options that we present to families, not all of which everyone will be eligible for. And they all have different risk profiles. And I really think the choice of a particular therapy has to be a risk-benefit decision and a shared decision-making process between the physician and the family.

Dr Nevel: What is going on in research in this area? And what do you think will be the next big breakthrough? I know before we started the recording you had mentioned that there's a lot of things going on that are exciting. And so, I'm looking forward to hearing more.

Dr Jayaraman: Of course. So, I'll be as quick as I can with this. But I mentioned that next-generation Exon skipping therapies, I think the hope is that they will be better at delivering the Exon skipping to the target tissue and cells and that they might be more efficacious. I'm also excited about next-generation gene therapies that might target muscle more specifically and hopefully reduce the off-target effects, or combination use of gene therapies with other immunosuppressive regimens to improve the safety profile and maybe someday allow redosing, which we cannot do currently. Or potentially targeting the satellite cells, which are the muscle stem cells, again, to improve the long term durability of these genetic therapies.

Dr Nevel: That's great, thank you for sharing. Thank you so much for talking to me today about your article. I really enjoyed learning more about the dystrophinopathies. Today I've been interviewing Dr Divya Jayaraman about her article on the dystrophinopathies, which she wrote with Dr Partha Ghosh. This article appears in the October 2025 Continuum issue on muscle and neuromuscular junction disorders. Please be sure to check out the Continuum Audio episodes from this and other issues. Also, please read the Continuum articles for more details than what we were able to get to today during our discussion. Thank you, as always, so much to the listeners for joining us today, and thank you, Divya, for sharing all of your knowledge with us today.

Dr Jayaraman: Thank you so much for having me on the podcast.

Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.