You’ve all heard my rant about the importance of not calling XLH “a form of rickets,” so I’ll keep it brief here. I mean, it’s fine to say in conversations with friends or family, where accuracy doesn’t matter, and it’s easier than getting into all the details. But with clinicians and researchers, it’s important to use more accurate terminology. Rickets is, to anyone with medical training, a symptom that ONLY occurs in children before their growth plates heal, so calling XLH a form of rickets completely ignores all the adult patients and their symptoms.
So you can probably imagine my reaction when I saw this headline: “Alopecia with Vitamin D dependent rickets: A case report.” Except, when I read the actual article, I realized the title was mostly correct. Unlike the old “vitamin D RESISTANT rickets” diagnosis that XLHers often got in the past, which was totally incorrect in terms of the cause of our symptoms, there is a real condition known as Vitamin D-DEPENDENT rickets, which is caused by problems with vitamin D metabolism, so it can be treated with vitamin D supplements. It’s still a problematic name, since I’m fairly sure it’s a life-long condition, not a purely pediatric disorder, which got me to thinking about how much of medical names for conditions are outdated.
As scientists get to the root cause of the problems (like the over-abundance of FGF23 in XLHers), without updating the old name, more and more rare diseases end up with names that don’t accurately describe the condition. It may not matter when the disease is named after a person, like Meniere’s disease is, since the name doesn’t carry with it any false information. (I wonder, though, if someday it will turn out that Meniere’s is actually multiple conditions, each with a potentially more accurate name that describes the underlying causes, some genetic, some not, so even with people’s names, they can become outdated.) And with names that purport to describe the underlying cause, like “vitamin D resistant rickets,” keeping the old nomenclature can perpetuate false information about the condition.
Sometimes, I think we need a wholesale re-ordering of the taxonomy and naming of disorders to make them more accurate. You’d think that scientists, of all people, would want them to be accurate! For XLH, the organizational tree should start with hypophosphatemia, and then subdivide between non-genetic causes (nutrition, etc.), and genetic causes. Instead, it often starts with rickets and then subdivides between non-genetic causes and genetic causes. Which, of course, leaves out adults and our symptoms, or at least indicates that we are less important than pediatric patients, even though there are likely three times as many of us as there are XLH kids!
Occasionally, there is some change in the nomenclature, as with ENPP1 deficiency, a genetic form of hypophosphatemia caused by something other than overproduction of FGF23. It used to be lumped under the general term of GACI (Generalized Arterial Calcification of Infancy), and anyone who survived infancy got lumped in with XLHers for treatment with phos/calcitriol, but now that its actual cause is known, the ENPP1 name is becoming more widely used.
I think that’s a trend we’ll see more and more, as specific proteins (like ENPP1) and specific genetic mutations are identified and used as the name of the disorder. It’s already happening with cancer. It’s not a medical field I know much about, but you’ve probably seen that what was once considered a single disease, “cancer,” is now viewed as different diseases, depending on which body part/system it affects. And even within a given part/system, the diseases are divided further and given separate labels, often reflecting the underlying biochemistry. For example, the category of “breast cancer” is no longer considered to be one condition, but several, depending on a variety of factors, including whether the cells are positive or negative for HER2, a hormone that’s involved in breast cancer.
So why the resistance to renaming rare diseases? I understand it’s a shorthand reminder for clinicians who were trained before the new name came into vogue, but seriously, how many clinicians are still practicing who were attending med school before research established (in the late 1970s, I believe) that XLH was a problem of phosphate-wasting, almost nothing to do with vitamin D? That’s around fifty years ago, so those students would be in their eighties now! Are we really saying that med schools are so bad at their jobs that they aren’t teaching students the latest information, so recent graduates still think of XLH as a vitamin D problem? I surely hope not! And even if the clinicians were given incorrect information in the last century and they are still practicing medicine in a field that’s relevant to XLH, have they not attended a single continuing medical education program in the last twenty-plus years that would have introduced them to the name, XLH, so it shouldn’t come as a big surprise to them when it’s used in journal articles now? Can’t we at least drop the VDRR name in most settings, if not the hypophosphatemic rickets name?
And why do we keep dragging along the old names anyway? I’m guessing it’s mostly jsut habit, without considering the harm it might do by perpetuating false beliefs. I can sort of understand wanting to maintain a historical record, perhaps of benefit to researchers looking for early data on the condition, who might not find what they’re looking for if they don’t search under the old names. But if it’s legitimately important to keep those old names, we need something to indicate that while these names were once used, they are massively misleading, and not at all reflective of the current understanding of XLH. Otherwise, merely mentioning these names can, for a clinician otherwise unfamiliar with the rare disorder, perpetuate the myths inherent in those old names.
I don’t need a hero, I just need a footnote! Something that says the old name is included just for historical reasons, and everyone should be aware that it was massively incorrect about the actual condition.
I suppose it would take a hero to lead the way in noting whenever old medical terminology is problematic. The good news (to carry over last week’s theme) is that I do think there are several candidates for heroism in the new crop of scientists working on XLH and advocating for patients. I’m looking forward to seeing who will be the first to tackle this particular issue.
**
Please note that the author is a well-read patient, not a doctor, and is not offering medical or legal advice.
If you’d prefer to read this blog as a newsletter, sent straight to your inbox, please sign up here.