Clinical feature: 

Definition: Rickets is defined by a deficiency in vitamin D resulting in growth retardation and bone deformity.

Pathogenesis: The disease is most often caused by inadequate intake of vitamin precursors or insufficient exposure to sun light. Some rare hereditary forms are due to mutations of the vitamin D activating enzyme (type 1) or the vitamin D receptor (type 2).

Diagnostics: 

Strategy: The differentiation of rickets starts with vitamin D (colecalciferol) substitution when hypercalcemia is excluded. In cases where in spite of this therapy a low concentration of 1,25-dihydroxy vitamin D3 can be found and a kidney disease can be excluded a defect in 1-alpha hydroxylation can be suspected. In cases where 1,25-dihydroxy vitamin D3 is normal a vitamin D receptor defect must be taken into account.

Literature: 

Kato S et al. (2002) Molecular genetics of vitamin D- dependent hereditary rickets.
et al. (2000) Autosomal dominant hypophosphataemic rickets is associated with mutations in FGF23.
Econs MJ et al. (1997) Autosomal dominant hypophosphatemic rickets/osteomalacia: clinical characterization of a novel renal phosphate-wasting disorder.
Scriver CR et al. (1977) Hypophosphatemic nonrachitic bone disease: an entity distinct from X-linked hypophosphatemia in the renal defect, bone involvement, and inheritance.
Scriver CR et al. (1981) Autosomal hypophosphataemic bone disease responds to 1,25-(OH)2D3.