[Osteomalacia following intravenous iron suppletion].

BACKGROUND

Ferric carboxymaltose (FCM) is highly effective in supplementing iron-deficiency anemia and frequently used. However, it can severely interfere with the phosphate metabolism.

CASE DESCRIPTION: A 63 year old man with iron-deficiency anemia due to hereditary hemorrhagic telangiectasia was treated with intravenous FCM. After initiation of the FCM he developed generalized bone and muscle pain as well as insufficiency fractures. Treatment with colecalciferol was started. However, the bone pain increased and further investigation showed a hypophosphatemicosteomalacia with high urine phosphate loss suggesting renal phosphate wasting. Serum FGF23 level was increased confirming the diagnosis of FGF23 mediated hypophosphatemicosteomalacia induced by intravenous iron suppletion.

CONCLUSION

FCM injections may cause FGF23 mediated hypophosphatemia already 4 weeks after suppletion. Therefore it is recommended that serum phosphate levels should be checked frequently. In patients developing hypophosphatemia, a non-maltose form of iron suppletion must be started as well as active vitamin D.