The flow of newly reported research continues strong, and I almost missed this one until a patient advocate in Australia (Hi, Sandy!) shared it: “The ankle in XLH: Reduced Power, Motion and Quality of Life,” in the March issue of Frontiers in Endocrinology. The whole article is available to read at the link, and I highly recommend it. I believe it’s the first time any published article has looked closely at the XLH ankle this comprehensively, with most attention generally focused on the hips, knees and spines.
I hadn’t really thought about XLH ankles in any great depth, which is a bit ironic, since I have significant calcification/pain/etc. in one ankle. I had relatively mild symptoms as a kid, with much less of the bowing and misalignment than many of us have, so my ankles were reasonably okay until well into adulthood (it only became a problem for me sometime in my forties, I believe). On reflection, it’s obvious that ankles would present issues for XLHers with more severe, early bowing, so that the lower leg meets the foot at an uncomfortable angle.
According to this article (which cites another article that I swear I read when it was first published but for some reason this bit of info didn’t stick in my brain): “Ankle pain is the second most common site for joint pain in children, following knee pain, and accounts for third place of the lower limb in adults with XLH.”
The other takeaway for me is what is summarized in the title — that the ankle issues (pain, calcification, malformation) have a multitude of effects on the patient, from the reduced power of the ankle to the adverse effects on the gait (motion), and ultimately the reduction in quality of life. And of course, each of these elements exacerbates the others!
I think you’ll find it interesting reading, and I swear I’m not highlighting this article just because the authors avoided the pitfalls of conflating XLH with rickets! (I’ve since corresponded with one of the authors, who seems to really listen to patients and absorb our perspective. It’s so great to know that we’re being heard!)
A couple other articles of interest:
“Osteomalacia in Adults: A Practical Insight for Clinicians” has some good suggestions for distinguishing between XLH and some common misdiagnoses (like ankylosing spondylitis).
“Burosumab Versus Phosphate/Active Vitamin D in Pediatric X-Linked Hypophosphatemia” offers solid evidence that burosumab is preferable to the (terrible) old phosphate/calcitriol treatment (which I refuse to call “conventional” any longer), regardless of phosphate/calcitriol dosage: “Switching from conventional therapy to burosumab improved rickets and serum alkaline phosphatase more than continuing either higher or lower doses of phosphate or active vitamin D.” Note that I only have access (at the link above) to the abstract, not the data itself.
This article on burosumab is particularly important for improving patient access to burosumab, I think. Regulatory agencies always seem to want to see this head-to-head comparison, and some are dismissive of patients’ testimony on the topic. The more data we have that burosumab is superior, the closer we get to burosumab being the default treatment for kids.
We need similar data for adults too, but publishing the pediatric research is a good first step. It will be difficult to gather really clear data on adults, since the physical changes as a result of treatment are less easily identified and measured in fully-formed adult bones than in growing pediatric bones. In the absence of such adult data, we’ll need to argue that if burosumab improves bone mineralization and healing (and reduces fatigue and muscle dysfunction) better than phos/calcitriol for kids, then it’s more likely than not that burosumab also improves bone mineralization and healing better than phos/calcitriol in adults (and that’s even without comparing the lack of side effects from burosumab with the significant side effects from phos/calcitriol).
Also, take a look at the list of authors for the article on burosumab. It’s great to see experts from all over the world! You will likely recognize the name of Dr. Erik Imel, who has spoken at XLH patient events, including the Symposium on Hypophosphatemia and at least one XLH Day. I’ve also heard good things about Dr. Leanne Ward in Canada. I’m not familiar with the other authors, but love seeing representatives from so many countries working together: Sweden, Australia, England, Japan, South Korea, and Austria!
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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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