Longitudinal growth in X-linked hypophosphatemic rickets

X-linked hypophosphatemic rickets (XLH) is the most prevalent form of inherited rickets associated with a disorder of phosphate homeostasis. It is caused by deactivating mutations in the PHEX gene. The clinical manifestations are characterized by growth retardation, skeletal deformities, osteomalacia, dental abscesses, and bone pain. Laboratory findings show a hypophosphatemia due to tubular phosphate wasting, elevated bone metabolic parameters, and a resulting inappropriately normal 1,25-dihydroxyvitamin D due to an abnormal vitamin D metabolism. The clinical features show a broad phenotypic variation even within the same family to the extent of some patients growing almost normally and others reaching a final height of -4 SDS or less. Some factors could be identified to show a certain impact on growth, while others remain elusive. Many circumstances of the pathophysiology and factors influencing growth have not yet been understood. The conventional treatment comprises high doses of phosphate and active vitamin D with recent studies demonstrating a positive effect of growth hormone.