XLH is a rare disorder, affecting 1 in 20,000 individuals, it is developed when the mineral phosphorus is wasted into urine. This “wasting” can cause low phosphorus levels in blood called hypophosphatemia
XLH is a rare disorder, affecting 1 in 20,000 individuals, it is developed when the mineral phosphorus is wasted into urine. This “wasting” can cause low phosphorus levels in blood called hypophosphatemia. Phosphorus is a mineral found in bones that is responsible for building and repairing bones and teeth, making muscle contract, supplying the cells with energy and essential for normal growth and development. Bones release, stored phosphorus to try to keep blood levels normal but the loss of phosphorus from bones leads to soft weak bones also called rickets, where mineral deficiency deforms the growth plate, and osteomalacia, where poor mineralization weakens the bone structure.
XLH is caused by a defect (a mutation) in a gene called PHEX [pronounced “Feks”] gene on the X chromosome. This gene is responsible for regulating phosphates in the body. The genetic change prevents the kidneys from processing phosphorus correctly. Problems with PHEX, lead to increased production of fibroblast growth factor 23 (FGF 23), which blocks the kidney’s ability to hold on to phosphorus. As a result, too much phosphorus leaves the body in the urine, which is also known as “phosphate wasting”.
Although there can be other reasons for rickets, such as vitaminD deficiency, XLH is one of the few causes that is inherited, meaning it is passed down from parent to child on a mutated gene. In about 20% of cases, a person develops XLH without any family history.
In the past, XLH was called “hypophosphatemic rickets" or “vitamin D-resistant rickets,” because it resembles the bone problems of vitamin D deficiency but doesn’t respond to vitamin D supplementation. However, there is now a different disorder with this name, caused by problems of vitamin D action. XLH has also been referred to as “phosphate diabetes,” due to the urinary wasting of phosphorus.
Term you should know:
Hypophosphatemia: low blood phosphate
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