Mice with DMP1 deficiency develop rickets and osteomalacia, including growth plate defects, abnormalities in osteocyte differentiation and the osteocytic canaliculi–lacunae system, an increase of FGF23, mild hypercalcemia with normocalciuria, phosphaturia and severe hypophosphatemia. The gene discussed is FGF23; the disease is hypophosphatemia.