For what feels like forever, I’ve been hoping for more research into XLH enthesopathy (calcification of tendons and ligaments), and now we finally have some: “Prevalence of Enthesopathies in X-Linked Hypophosphatemia—an Explorative Ultrasound Study.”
It’s been known for a long time, at least among experts, that XLH patients have a high prevalence of enthesopathy (at least since 2011 when the “Clinician’s Guide to XLH” was published: “Many adults with XLH have enthesopathy, which does not improve with treatment.”) but there hasn’t been a lot of information about exactly how common it is or a full accounting of where it occurs on the body.) What I find particularly interesting in this new article is that the researchers knew enough to not just assume that the symptom was limited to the lower body, and instead looked at likely (weight-bearing) sites in both the lower and upper body.
Most of the results aren’t surprising to patients—nearly all XLH patients develop enthesopathy over time, more in the lower body (85% of patients) than upper body (50% of patients)—but it’s important to have data confirming our experience. Especially, as noted, with respect to the enthesopathies not being limited to the lower body, since too many clinicians assume only the lower body is affected. I highly recommend taking a look at Figure 2A which illustrates the locations where the most common enthesopathies occur. It struck me as a very useful page to print if you need to discuss your enthesopathies with a clinician, so you can be sure you and the clinician are talking about the same things. I get lost in the anatomical terms, but it would be easy to point to a spot and say, “This is where I’m having problems.”
One area that I think needs more work (outside the scope of this study) is on the issue of pain in the context of enthesopathy. The study found only “weak, non-significant correlations between the total number of enthesopathies and both pain inference … and pain severity ….” One thing I’ve noticed is that once an enthesopathy has happened and is stable, it doesn’t hurt, and it’s been a while since most of mine formed, but I distinctly recall some of them hurting WHILE they were forming. I don’t know if it was actually the calcification process that hurt or if the pain was due to an underlying bone problem that triggered the calcification, just that the area was painful at a time when the enthesopathy was just beginning. I don’t know how one could even study that, since we tend to have random pain that has no visible physical cause, so it would be hard to identify when a pain was due to the enthesopathy process and when it was due to some other cause.
Before I forget, I want to point out the authors’ acknowledgment of the Austrian XLH Alliance for its support of this research, a nice example of true patient engagement rather than patient decoration. I frequently rant about how too few researchers engage with patient advocacy groups, and even when they do engage, they often fail to acknowledge the value of that engagement. It’s nice to be able to point to an example of how the patient voice was properly acknowledged!
And now back to the topic of enthesopathy—if you (or your clinician) want to read more about it, I recommend checking out this article on how and why these enthesopathies happen: “The Enthesopathy of XLH Is a Mechanical Adaptation to Osteomalacia.” There’s also “Osteoarthritis, Osteophytes, and Enthesophytes Affect Biomechanical Function in Adults With X-linked Hypophosphatemia.”
Now, the only thing that’s really missing is discovery of the biochemical process of soft-tissue calcification, so we can develop a treatment to reverse it! This is an area where research into XLH could lead to treatment that can benefit not just us, but the wider population. Enthesopathy is a potential problem for the general population in old age, but the way we experience it at a much earlier age makes us ideal research subjects!
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Please note that the author is a well-read patient, not a doctor, and is not offering medical or legal advice.
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