Hypophosphatemic Rickets, also known as hypophosphatemia, is a genetic condition characterized by low phosphorus levels in the blood and increased phosphorus wastage through excretion in the urine.  Since the condition is X-linked, more males are affected than females. 

The causative gene has been identified to be the PHEX gene on chromosome X. Mutations in this gene have been found to cause proteolytic degradation of at least one extracellular matrix glycoprotein that in turn leads to increased phosphate excretion at the proximal tubule. Bone mineralization is thus impaired, leading to the defects in the skeletal system.