X-linked Hypophosphatemia

Also known as: Familial Hypophosphatemic Rickets; Vitamin D Resistant Rickets


X-linked hypophosphataemia is a rare condition that causes low phosphate levels in the blood (hypophosphataemia), associated high phosphate excretion in the urine (hyperphosphaturia), and symptoms of rickets such as bowed or knock-kneed legs. Dental problems are also common. The gene that is changed (mutated) in this syndrome is called PHEX, and is located on the X chromosome. Diagnosis is made by blood tests, which show a low phosphate level and high alkaline phosphatase level. Treatment  involves improving the blood phosphate level using oral phosphate supplements, and an active vitamin D hormone such as  1-alpha D3 (alfacalcidol) or 1,25 D3 (calcitriol). Regular blood tests for phosphate and alkaline phosphatase levels, and ultrasound examination of the kidneys to check for calcium crystals as a side-effect of Vitamin D treatment, are part of the standard care associated with this condition. Occasionally, surgery is needed to shorten, lengthen, or change the angle of a leg bone. The gene causing the condition can be inherited, or the condition can occur sporadically (with no family history). Affected families should be referred to a specialist centre for information and support.

This overview is intended to be a basic description of the condition. It is not intended to replace specialist medical advice. We advise that you discuss your child’s case with a qualified medical professional who will be able to give you more detailed information.


Medical text approved January 2013 by Dr C Reid, Paediatric Nephrologist, Evelina Children’s Hospital and Dr M Champion, Contact a Family Medical Advisory Panel.

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Email: via website
Website: xlhuk.org

XLHuk is a registered charity in England and Wales no.1182964. Their mission is to promote XLH and related disorders, awareness and education for affected families, medical professionals and the community at large within the UK.

Group added November 2019.

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