This week I’m sharing some light beach reading for your summer vacation. Okay, I lied, and it’s not really light reading, but it’s still worth your time if not perhaps while on vacation! It’s unlikely that your clinicians (unless you see top experts) will know about the most recent XLH research, since there’s a lot of it happening these days. You need to know what’s out there, even if you don’t understand every word of the articles, so then you can alert your (or your child’s) medical team to new information.
Today’s articles are about the gait issues that persist into adulthood, regardless of early surgical or pharmacological intervention. That may change in the future, when kids who started on burosumab during childhood become adults, but for now, it’s pretty well established, among both patient anecdotes and peer-reviewed research, that even patients who received “state of the art” treatment with surgery and/or phosphorus/calcitriol have persistent gait issues in adulthood.
First, in case you missed it before, is “Osteoarthritis, Osteophytes, and Enthesophytes Affect Biomechanical Function in Adults With X-linked Hypophosphatemia” from the Journal of Clinical Endocrinology and Metabolism.
The article gets somewhat technical, which makes it an intense read, but that’s also why the article is so important. We, the patients, know just how significant the adult symptoms of XLH are — the arthritis, calcifications, and the resulting mobility challenges — but until those symptoms are turned into data, the medical community can ignore them. This article does exactly what’s needed, turning the symptoms into data.
Patients have known for a long time that our childhood symptoms morph and progress in adulthood, despite the medical community insisting that we would go on to have normal health, with no ongoing challenges other than being short. The data in this article blow that belief completely out of the water (at least for anyone with an open mind).
Here’s the key findings from the abstract: “Enthesophytes, degenerative arthritis, and osteophytes were found to be consistently bilateral and diffusely present at the spine and synovial joints across participants, with predominance at weight-bearing joints. Passive [range of motion] in adults with XLH was decreased at the cervical spine, hip, knee, and ankle compared to controls [non-XLH study volunteers]. Gait analysis relative to controls revealed … physical restriction at the hip, knees, and ankle joints that translated into limitations through the gait cycle.”
In other words: all of our weight-bearing joints (and some non-weight-bearing) are arthritic and/or calcified, which affects those joints range of motion and our ability to walk normally.
Hardly normal health!
A subsequent study confirmed those findings. “Lower Limb Deformity and Gait Deviations Among Adolescents and Adults With X-Linked Hypophosphatemia” is in Frontiers in Endocrinology.
The later study included more patients and a wider age range (teens to over 60 years old), but with a lower mean age (29 versus 59). Nevertheless, the results were consistent across both studies, showing ongoing gait abnormalities that lead to significantly decreased quality of life in adulthood, consistent with the previous article.
The later study also seems to confirm something that we’ve been saying for years — that we’re so used to certain aspects of our disorder that we don’t even notice their effects, which in turn means that the extent of our symptoms is under-reported. The article notes that earlier research had indicated that patients who underwent corrective surgery, “did not complain of significant residual torsional malalignment even though diaphyseal bowing was not completely corrected.” But the data in the new study showed that the malalignment “might have significantly contributed to gait deviations in adults with XLH, thereby causing burden of disease.” We don’t complain about a lot of things, because they’re just background noise, not things we’re consciously aware of, even as they are, in fact, causing us harm.
I found it interesting that the authors of the later study called for more research into foot and ankle deformity. Most of the emphasis in discussions of XLH is focused on knees and hips, but feet and ankles are also involved, and, in my experience, can worsen the issues at the knees and hips.
And finally, I learned something new about how best to talk about one symptom of XLH: the “waddling” gait. As the authors noted, the connotations of “waddling” can be embarrassing for patients, so they adopted a more neutral term, “lateral torso lean,” which is increased in the majority of XLHers. Yeah, it’s a mouthful, like everything else related to XLH, but if we can learn to say “x-linked hypophosphatemia” and “enthesopathy” without stumbling over the syllables, we can say “lateral torso lean.”
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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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