[Genetic basis for skeletal disease. Hereditary rickets]

Hereditary rickets is caused by inborn error of vitamin D activation, vitamin D receptor (VDR) function or increased urinary phosphate excretion. Loss-of-function mutation of 1alpha-hydroxylase gene and loss-of-function mutation of VDR gene result in vitamin D-dependent rickets type I and type II, respectively. X-linked hypophosphatemic rickets (XLH) is the most common type of hypophosphatemic rickets, and autosomal dominant (ADHR) and negative (ARHR) types are rare. The diagnosis may be sometimes difficult and increasing cases of vitamin D deficiency must be distinguished.