There’s a new article about blood pressure in pediatric XLHers, “Office Blood Pressure and Obesity in Children with XLH.”
The article starts off badly by calling XLH “the most common inherited form of hypophosphatemic rickets.” I’m cutting the authors a little slack, since they’re focused specifically on pediatrics (only kids can get rickets), but it’s a bad habit to get into, and it undermines the whole-body nature of XLH in kids, implying that the rickets symptom is the entirety of the condition.
Beyond that, I’m not really sure how useful the article is. The authors found a correlation between BMI and elevated blood pressure, and possibly (but not quite at the level of statistical significance) a correlation between the old phosphorus/calcitriol treatment and elevated blood pressure (which makes sense, because the phos supplements contain salt and salt elevates blood pressure). Oddly, if I read it right, they also found higher BMI in patients on burosumab than patients on the old treatment, but one of the acknowledged limitations of the study was that most of the patients on the old treatment had milder symptoms than those on burosumab. They don’t say it outright, but having milder symptoms would, it seems to me, result in increased activity and therefore less extra weight, so the difference in BMI can’t be attributed to the type of treatment with any confidence. To really know if the extra weight is related to the treatment regimen, we’d need to see the data on kids with similar severity of symptoms but with different treatment regimens.
The bottom line on this article is that it’s (almost) always good to have more data, but I don’t know that it’s possible to draw any useful conclusions from it. The article basically just concludes that a higher percentage of XLHers are overweight/obese than the general population (which we knew already), and a similarly higher percentage of us have elevated blood pressure (which patients knew, even if it hadn’t been documented), so maybe the two (excess weight and elevated blood pressure) are related. Much like a previous article on XLH pain, it feels like the authors just went for the easy/simple answer instead of what’s likely to be a much more complicated and nuanced answer.
I’d like to see a larger study (weight and BP could be collected in a natural history study), along with some validation of whether BMI is an appropriate measure for XLH patients, or if our often over-sized bones require a revision to the healthy weight range associated with BMI.
I’d also like some assurance that the blood pressure readings were consistently taken properly (seated, after resting for 5 minutes, correct size cuff, proper body position, etc.), since I know from personal experience that the readings are seldom done following best practicies (virtually never in my case — the last one was done standing, no rest, no body positioning), and the bad practices almost always lead to exaggeratedly high numbers.
I’d also be interested in information correlating the patient’s reported pain on the day of the blood pressure reading, since pain can elevate blood pressure. The study mentions the issue of “white coat syndrome” (anxiety during medical appointments) possibly leading to high blood pressure in the doctor’s office, and a lot of patients with a rare disorder develop anxiety both before and during doctor’s visits, so it would be useful to compare the office readings with home readings to see if the patients in the study have elevated blood pressure all the time or only, as is normal, during times of stress.
This article might be worth sharing with your (or your child’s) clinician if you (or your child) has elevated blood pressure and is unaware that it’s a common symptom in the #XLH community. On the other hand, if you (or your child) have been told by a clinician that all you need to do is lose weight, and all your health problems will go away, then this article will only reinforce the clinician’s totally misinformed opinion.
Yeah, I’m feeling a bit cynical these days. But I’m willing to bet that most of you, if you’re so much as a couple of ounces over an ideal weight (and even if it is indeed a healthy weight for you), have been given some variation on the “just eat better and exercise more, and you’ll lose weight” advice that makes me homicidal. Fortunately, I get to kill people in my novels, which lessens the urge to kill people in real life.
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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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