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Genetic and Rare Diseases Information Center (GARD)

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Hypophosphatemic rickets

Other Names for this Disease
  • HYP
  • Hypophosphatemia, X-linked
  • Hypophosphatemia, vitamin D-resistant rickets
  • Vitamin D-resistant rickets, X-linked
  • XLH
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What causes hypophosphatemic rickets?

Hypophosphatemic rickets can result from changes (mutations) in several different genes. Mutations in the PHEX gene, which are responsible for X-linked hypophosphatemic rickets, are the most common. Mutations in other genes cause the less common forms of the condition. Hypophosphatemic rickets is characterized by a phosphate imbalance in the body. Phosphate has many functions, but it plays a very important role in the formation and growth of bones in childhood and helps maintain bone strength in adults. Phosphate levels are mainly controlled by the kidneys. The kidneys normally take excess phosphate out of the body in the urine, and they reabsorb phosphate into the bloodstream when more is needed by the body. However, in people with hypophosphatemic rickets, the kidneys cannot reabsorb the phosphate effectively, and too much of the phosphate leaves the body in the urine. As a result, not enough phosphate is available in the bloodstream for normal bone development and maintenance.[1]

The genes associated with hypophosphatemic rickets are involved in maintaining the proper balance of phosphate in the body. Many of these genes, including the PHEX gene, may directly or indirectly regulate a protein called fibroblast growth factor 23 (produced from the FGF23 gene). This protein normally inhibits the kidneys' ability to reabsorb phosphate into the bloodstream. Gene mutations increase the production, or reduce the breakdown, of fibroblast growth factor 23 and the resulting overactivity of this protein reduces phosphate reabsorption by the kidneys, leading to hypophosphatemia and the other features of hypophosphatemic rickets. To see a list of genes associated with hypophosphatemic rickets, click here.[1]
Last updated: 1/10/2011

  1. Hereditary hypophosphatemic rickets. Genetics Home Reference. September 2010; Accessed 1/10/2011.