I’m back from my summer hiatus with some exciting news and more ideas for future posts than I can fit into the remaining weeks in the year!
You’ve probably noticed that I pretty quickly abandoned my original plan to talk about the three FAQ sheets I think we need and no one else is creating (two with the basics for primary care providers—one for adult patients and one for kids—and one for aging with XLH). I’m still working on them, and hope to have the page on what primary care providers need to know about coordinating the care of adult XLHers later this month. Then the kids’ version in October and the information on aging with XLH in November.
Yeah, best laid plans and all that. But I’m really hoping to settle down and get you some drafts of those three documents, so you can tell me what I’ve missed.
I’ve also got a BUNCH of journal articles to share and review over the remainder of 2026, plus some information on parathyroids, hearing loss, future research, and, finally, collaboration with other rare disease communities.
Today though, I want to share a bit about a new research study that I’m really excited about. In a sense, it’s actually an old study, because it’s a repeat of the key pieces of the gait, mobility, and range of motion study that was reported on in “Osteoarthritis, Osteophytes, and Enthesophytes Affect Biomechanical Function in Adults With X-linked Hypophosphatemia.” The original study happened at Quinnipiac University’s Frank Netter School of Medicine eleven years ago (spring of 2015), before the Phase 3 clinical trials for burosumab began, and involved (among other things) full-body x-rays, gait analysis, and range-of-motion measurements. The conclusions were hardly surprising—adults with XLH have widespread calcifications in the spine and major joints, decreased range of motion in the spine and major joints, and our gait is adversely affected by those calcifications and decreased range of motion—but it was absolutely critical to document these issues objectively to support patient anecdotes.
The new study (also at Quinnipiac) will repeat those three portions of the original study with the exact same patients (and the same physical therapist doing the range-of-motion testing for consistency’s sake). Having the same patients is important, given the small number of patients involved (under ten), so they’ll be comparing specific patients’ progression, not looking at an amalgam of patients, which could be confusing, given the wide range of symptoms within the XLH community.
The goal this time is a little different from the first study. It’s no longer necessary to establish the existence of widespread calcifications, decreased range-of-motion, and gait abnormalities, which the original did (although the new data will undoubtedly confirm those original observations). Instead, the point is to see how those symptoms have changed over the course of ten-plus years. Patients know, from our lived experience, that XLH is a progressive disorder, but we haven’t had data before now to show just how progressive it is, and as a result, I think the progressive nature of XLH is under-appreciated. We’re beginning to see data from natural history studies, which is great, but they mostly consist of patient’s self-reported symptoms and don’t have the (relatively) objective evidence of x-rays and a physical therapist’s measurements of range of motion.
The original study happened before there was widespread access to burosumab, and indeed, there was only limited access the next three years (until spring 2018). I believe several (if not all) of the patients in the study were also in the burosumab clinical trials which began a few months after the original study. For those patients who were on burosumab for the ten years between the two sets of tests, we’ll essentially be able to see the best-case scenario for the progression of the disorder, rather than the much worse progression that we know occurred without effective treatment. My hope for treatment has always been to plateau my symptoms (the ones that can’t be reversed, like the calcifications), and this study will give us at least a hint of whether that’s happening with burosumab over the long term.
Regardless of the specific outcomes of this study, I expect it will give us new insights into the progression of XLH in older adults, and will inspire many more conversations about the importance of treating XLH preventively, rather than reactively. I’ll let you know when the results are published!
Meanwhile, I hope you had a lovely summer and are as energized for the remainder of the year as I am!
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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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