Saccharated ferric oxide-induced osteomalacia in Japan: iron-induced osteopathy due to nephropathy.

Saccharaed ferric oxide (SFO)-induced osteomalacia develops when excessive SFO infusions are administrated to patients with anemia for prolonged periods for a few years. The small particles and almost neutral saccharide of SFO filter through the glomerular tufts into the renal tubules, resulting in impairment of proximal renal tubular function, particularly renal reabsorption of phosphate and 1alpha-hydroxylase activity, resulting in decreased serum levels of phosphorus and active vitamin D, both of which lead to development of hypophosphatemic osteomalacia. Furthermore, SFO, at concentrations attainable in serum, exacerbates the osteomalacia by inhibiting bone formation directly. In contrast to itai-itai disease, another iatrogenic osteomalacia due to cadmium nephropathy [44], the proximal renal tubular function impairment induced by SFO is reversible simply by discontinuing the nephrotoxin, which is followed by improvement of all the clinical manifestations, except bone deformities. So far, SFO-induced osteomalacia, that is, SFO-induced osteopathy due to nephropathy, has been reported only in Japan, probably due to the lax surveillance system of the health insurance scheme. All physicians who prescribe SFO should be aware of its severe adverse effects. We hope that such iatrogenic osteomalacia caused by abusive infusion of SFO will never again be reported in our country.