PHEX gene

X-linked hypophosphatemic rickets is caused by abnormal reabsorption of phosphate in the proximal renal tubule, resulting in excessive excretion of phosphate and hence hypophosphatemia. There may also be blunting of the normal increase in calcidiol 1 -hydroxylase activity in response to hypophosphatemia. The gene responsible for the condition has been identified (the PHEX gene) its product is a membrane-bound endopeptidase that normally acts to clear the hormone phosphatonin from the circulation. Phosphatonin acts to decrease the activity of the sodium/phosphate cotransporter in the kidney (Drezner, 2000). 

Drezner MK (2000) PHEX gene and hypophosphatemia. Kidney International 57,9-18. 

Several disorders of tubular phosphate handhng have been described. The best known of these is X-linked dominant hypophosphatemic rickets (previously known as vitamin D-resistant rickets). This disorder arises because of a defect in the PHEX gene. A defect of the sodium-dependent/ phosphate co-transporter has also been described, giving rise to autosomal recessive hereditary hypophosphatemic rickets with hypercalciuria. The molecular biology of tliese and other renal phosphate transport disorders has been reviewed. ... 

Dodge WF, West EF, Smith EH et al (1976) Proteinuria and hematuria in school children epidemiology and early natural history. J Pediatr 88 327-347 Drezner MK (2000) PHEX gene and hypophosphatemia. Kidney Int 57 9-18... 

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