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
properly causing the loss of phosphate in the urine (phosphate wasting). This leads to soft, weak bones.
A mutation in the PHEX gene on the X chromosome causes XLH, and inheritance is X-linked dominant. 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.
While XLH is usually an inherited disease, it can appear in an individual with no known family history.
What are the symptoms?
Patients with XLH have abnormal bone and tooth development. Many develop rickets, which causes knock-knees or bowing of the legs. Other symptoms include:
- unusual gait (waddling when walking)
- short stature or declining growth rate
- spontaneous tooth abscesses
- bone pain, muscle pain and weakness.
How do you diagnose it?
XLH is usually diagnosed in childhood, with the symptoms of XLH often apparent before a child begins to walk. But, XLH is often undiagnosed or misdiagnosed as simple Vitamin D deficiency because it is a rare genetic condition. In the average person, normal diets and sunlight exposure successfully treat Vitamin D deficiency and conditions like rickets, but for people with XLH, this does not work. Early diagnosis is extremely important for effective XLH treatment. XLH Australia Inc is committed to empowering XLH-affected individuals and their families to successfully advocate for their diagnosis.
Is there a cure?
You can’t cure XLH, but you can treat it. Treatment generally involves supplements of phosphate and high-dose calcitriol (the active form of Vitamin D), and can also include growth hormones, corrective surgery, and dental treatment.
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.
You can read some patient stories stories here. The video below explains XLH simply.