Table 2.

The genetic abnormalities associated with the various forms of hypophosphataemic rickets

Disease	Gene involved	Gene product	Serum FGF23	Serum 1,25(OH)2D
X-linked hypophosphataemic rickets	PHEX	Inactivating mutation in PHEX (endopeptidase)	Generally increased	Within normal range or decreased
Autosomal dominant hypophosphataemic rickets	FGF23	Activating mutation in FGF23 (phosphatonin)	Variable—may be increased during symptomatic disease	Decreased
Autosomal recessive hypophosphataemic rickets	DMP1	Inactivating mutation in DMP1 (involved in mineralisation)	Increased	Within normal range
Hereditary hypophosphataemic rickets with hypercalciuria	SLC34A3	Inactivating mutation in NaPi-IIc (renal Na-Pi cotransporter)	Not known	Elevated