X-linked hypophosphatemia (XLH) is an inherited genetic disorder that is characterised by low 
levels of phosphate in the blood. The kidneys of a person with XLH do not process phosphate
A change in the PHEX gene on the X chromosome causes XLH, and the condition passes down in an X-linked dominant pattern. This means women with XLH have a 50-50 chance of passing XLH on to their children while men will pass XLH on to all their daughters.
The long-term outlook varies. It depends on severity of XLH and whether there are complications. Some adults with XLH may have few medical problems, but others may experience significant discomfort or complications.