The key characteristic of XLH--low phosphorus in the blood—is the result of a mutation that inactivates one of the genes on the X Chromosome (hence the “X” in XLH). That means XLH is transferred genetically. However, XLH can appear in an individual with no known family history.

Symptoms of XLH can be apparent before a child begins to walk. But as a rare genetic condition, XLH is often undiagnosed or misdiagnosed as simple Vitamin D deficiency. In the average person, normal diets and sunlight exposure successfully treat Vitamin D deficiency and conditions like rickets, but this doesn’t work for people with XLH.

Early diagnosis is extremely important for effective XLH treatment. The XLH Network is committed to helping medical professionals diagnose XLH, and to empowering XLH-affected individuals and their families to successfully advocate for their diagnosis.

In comparing phosphorus levels to the charts below, it may be necessary to make a conversion. To convert mg/dL to/from mmol/L, SIGMA provides an inorganic phosphorus reference standard:
20mcg per ml equivalent to 645 nanomoles per ml
Since a deciLitre is 100 ml, this is the same as saying:
2000mcg/dL or 2mg/dL or 645 mcmoles/L or 0.645mmol/L
Therefore, 1mg/dL is the same as 0.322 mmol/L