Definition:

X-linked dominant hypophosphatemic rickets (XLH) is the most common form of hereditary rickets. XLH is characterized by a defect in renal phosphate transport, leading to phosphate wasting and hypo-phosphatemia, and by abnormal 1,25-dihydroxy vitamin D. Manifestations of XLH include rickets in children, short stature, and osteomalacia. Mutations in the PHEX gene have been identified as the cause of XLH. PHEX encodes a metalloprotease that is found in the cell-surface membrane of osteoblasts, osteocytes, and odontoblasts.