XLH is a genetic disorder, caused by a genetic variation (any of some six hundred that have been identified so far) on the X chromosome. And it’s dominant, so if the relevant variation exists in the DNA, the person has the disorder, so there are no “carriers” as are found in recessive disorders like the autosomal recessive hypophosphatemias. And yet, there are some XLHers (like myself) who have the genetic variation while neither parent does. It’s not a matter of skipping a generation. Instead, in these cases, the variation happened when the patient was in utero, and it’s referred to as a “spontaneous” or “sporadic” variation. Once the variation exists in the patient, it can be passed on to the patient’s offspring, just like it passes from patients who inherited their variation.
Scientists know that much. Everything else about spontaneous patients is less well understood, like how frequently it happens, and whether there’s any difference in symptoms between a spontaneous patient and a familial (inherited) one, and the ways that the lived experience may differ between the two subgroups.
Which led me to compare, in a totally unscientific formal way, my experience as a spontaneous case with the experiences of a couple patients who inherited their conditions. The first is fellow XLHer/advocate, Oliver Gardiner, founder of XLH-UK, and board member for both The XLH Network, Inc., and the XLH Alliance. The second is Kelly Rushing, a long-time regular member of The XLH Network, and as of this year, an elected board member of the Network.
Oliver is part of an extended family that includes fifteen XLHers, and Kelly counts 34 in her extended family! I grew up feeling like I was the only person on the planet with XLH, like I was “special,” even if in a negative way, while Oliver and Kelly were both surrounded by XLHers.
While it had to be reassuring to know they weren’t alone, the negative aspect of being part of multiple generations of XLHers is that Oliver and Kelly both saw, first-hand, the disabling and painful progression of the disorder in their older relatives.
That access (or lack of access) to community accounts for the biggest difference between my lived experience and that of Oliver and Kelly — they always had, and I never had, the ability to share information with both peers (siblings and cousins in the same general age range) and across the generations (parents, grandparents aunts/uncles). When they were asked how much XLH was discussed within his family, Oliver immediately answered, “All the time.” And that was true for all of his life, not just since he took on the role of a patient advocate. Kelly noted that XLH was discussed regularly among the directly affected members of her family (“It’s almost a unique language that we understand between us.”) but less often with the rest of the family.
We chatted a bit with them about other differences in experiences the two groups may have, stemming from the presence (or lack) of XLH-experienced community. The most obvious difference is that for many spontaneous patients, it’s more difficult/slower for the parents to get a diagnosis (although if the parent had a mild case, they may not have been diagnosed before the child is, so the diagnostic journey for the child will be delayed similarly to a spontaneous patient’s experience).
Other possible differences relate to the patient’s need for information and a sense of belonging or connection. As part of an extended family, Oliver and Kelly had plenty of people to turn to for education about XLH and coping tools for managing it. A spontaneous patient doesn’t have that resource, which may explain why, statistically speaking, they tend to be more engaged with groups like The XLH Network or the International XLH Alliance than inherited cases are. (Kelly and Oliver are both exceptions to the rule, and have been very engaged with patient advocacy, and once engaged, they bring with them not just their own experience and expertise, but their extended families’ experience and expertise) I’m not sure of the makeup of The XLH Network’s current board, but when I was on it, the vast majority of the members were spontaneous patients or the parent of a spontaneous patient. Speaking for myself, the need for information and connection, which I couldn’t get from family, was why I became active with the XLH Network, since, at the time, it was the only available source of patient-generated information.
There’s one other area where spontaneous and inherited patients’ experiences may differ. I grew up and tackled adulthood, completely unaware of the long-term impact of XLH. I was specifically told that there would be no future consequences, so I was free to do whatever I wanted with my life, when it came to physical activity and my choice of a career. Oliver and Kelly, on the other hand, could see for themselves the progressively debilitating nature of XLH. They both have at least one older relative with severely disabling symptoms. Faced with that evidence, they couldn’t help being aware of the possible challenges the future would bring, and the need to prepare for those challenges.
Oliver describes himself as being more cautious about his expectations for the future, of being aware of his physical/energy/fatigue limitations when he makes decisions relating to things like his career, while I never even considered the possibility that I would end up retiring early from a largely sedentary career as a lawyer, initially stepping back from full-time to part-time work, and then retiring from work entirely, because of my physical limitations (mostly related to pain and fatigue).
Kelly had a mixed reaction to the question of how her expectations of the future affect her in the present. She is totally aware that she might end up with a condition comparable to her most severely affected older relative’s degree of disability, and worried that she would become a burden to her husband (but, as she reports, “he wasn’t scared off”). At the same time, Kelly uses the knowledge of the future worst case scenario in the progression of her disability as motivation to take precautions against that physical deterioration. She says, “I felt I could make my own experience and try to be proactive as much as possible to prevent the debilitating effects of XLH.”
I think it would be informative to delve deeper into the psycho-social aspects of the differences in expectations between spontaneous and inherited XLH (something I believe Susan Faitos, Executive Director of the XLH Network is working on). We need research that is actually scientific, not me speculating on possible differences!
If there are differences in psycho-social challenges between the two groups, understanding more about them might inform both treatment (i.e., the occupational therapy and talk therapy elements of a comprehensive plan) and also the educational/social programs provided by advocacy groups (i.e., spontaneous patients may need more help with coping tips than the inherited patients who have gotten those tips and interactions from family). It might help patients with inherited XLH to be bolder in their lives, while also helping the spontaneous XLHers to be more realistic about their future. Over the years, I’ve heard from a number of XLHers who chose highly physically demanding careers, like nursing, only to find that, as much as they loved those careers, they had to retire early because their bodies simply couldn’t handle the physical stress.
Of course, a lot is changing in the XLH community, with the first effective treatment now on the market, and easier access to information and social interaction available online. It’s possible that XLH kids getting treatment today will, thanks to a lifetime of truly effective treatment, avoid the degree of disability experienced by the current older generations, so future patients won’t need to worry about whether they’ll be strong enough for their dream careers. And spontaneous XLHers won’t need to feel so all alone, since they can turn to their peers online. Kelly mentioned that the “unique language” she shares with her XLH relatives can also be found within her online community of XLHers. She noted that they (we!) truly understand what she means when she says she’s having bad day. “It’s just knowing that someone else knows what you have been dealing with on bad day, … that I do not have to explain details for someone else to understand.”
I’d like to think all of my questions about how to improve the lives of XLHers will become moot, thanks to the discovery and broad availability of a total cure. Until then, I’ll keep asking questions. I hope you will too!
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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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