As we were starting to construct the first-ever comprehensive natural history study of XLH, we realized it was a huge challenge, because, unlike some conditions, XLH affects pretty much every system of the body.
Scientists divide the human body into ten systems: 1) cardiovascular, 2) digestive, 3) endocrine, 4) integumentary/exocrine, 5) lymphatic/immune, 6) musculo-skeletal, 7) nervous, 8) renal/urinary, 9) reproductive, 10) respiratory.
It's immediately obvious that the endocrine, musculo-skeletal and renal (kidney) systems are relevant to XLH. The endocrine system regulates phosphorus and FGF23, muscle function and skeleton structure are adversely affected by elevated FGF23 and low phosphorus, and the kidneys are where the phosphate wasting occurs. Some digestive issues have been reported with phosphorus supplements. Some XLHers have nerve involvement as a secondary effect, when calcification impinges on nerves or when the patient has a Chiari malformation or syringomyelia (both of which may or may not be related to XLH).
What about the other, less obviously affected body systems? Wouldn't it be good to know if there's any correlation between XLH and an increased (or decreased!) risk of heart disease or elevated blood pressure? Between XLH and lung conditions? Between XLH and infertility? Or, more generally, and crossing a variety of systems: is there any correlation between XLH and an increased/decreased incidence in various forms of cancer? And what about pain and its treatment: what's the nature/extent of the pain, what's being prescribed and what, if anything, is most likely to be effective?
No one has those answers, in part because the questions have never been asked in a rigorously scientific manner. But we're hoping to change that soon!
The Network’s Registry and Data are part of the National Organization for Rare Disorders’(NORD) Natural History Program.We are thankful for NORD’s investment in the health and wellbeing of all rare disorder communities, including ours.