1,25(OH)₂D₃ is not the only D metabolite involved in the pathogenesis of osteomalacia

Three patients are described in whom there was no simple correlation between plasma 1,25(OH)₂D₃ concentration and the occurrence of osteomalacia. One patient had severe osteomalacia with high plasma 1,25(OH)₂D₃ and normal mineral ion product; the second had a normal mineral ion product and no evidence of osteomalacia even though plasma 1,25(OH)₂D₃ was undetectable; and the third had osteomalacia, low plasma 1,25(OH)₂D₃ and a reduced mineral ion product. In considering these data in the light of presently available information, it is concluded that osteomalacia can occur as a consequence of a lack of a vitamin D metabolite other than 1,25(OH)₂D₃, or as a consequence of a reduced mineral ion product, but not as a consequence of 1,25(OH)₂D₃ lack if the mineral ion product is normally maintained and other D metabolites are present. However, a deficiency of 1,25(OH)₂D₃ normally leads to a reduction in the mineral ion product hence 1,25(OH)₂D₃ deficiency may play a role in the development of certain forms of osteomalacia.