Mechanisms involved in the pathogenesis of rickets caused by a chronic low calcium intake. ANK = ankylosis protein; Ca = calcium; ENPP = ectonucleotide pyrophosphatase/phosphodiesterase; FGF 23 = fibroblast growth factor 23; PPi = inorganic pyrophosphate; PTH = parathyroid hormone; SIBLINGS = small integrin binding ligand, N linked glycoproteins; Tnap = tissue nonspecific alkaline phosphatase.