Failure of serum ferritin levels to predict bone-marrow iron content after intravenous iron-dextran therapy

The relation between serum ferritin levels and stainable-iron deposits in the liver, spleen, and bone marrow was investigated in 36 patients with chronic renal failure who died after being on haemodialysis for 1-103 months. Elemental iron (mean, 5450 mg) had been given intravenously as iron dextran to patients in a long-term subgroup, who had been on dialysis for more than 3 months. The results of semiquantitative histochemical assessment of tissue iron in slides obtained at necropsy (scale 0 to 4+) were confirmed by chemical analyses of tissue iron. Serum ferritin levels correlated well with the degree of hepatosplenic siderosis but did not always correlate with bone-marrow iron stores in these patients. Serum ferritin concentrations were raised in 10 marrow-iron-depleted subjects (mean, 1336 ng/dl). The paradoxical association of hepatosplenic siderosis with marrow iron depletion was observed in most of the patients on dialysis for less than 40 months. The histochemical data show that the bulk of intravenously injected iron dextran is taken up by the liver and spleen; that the hepatosplenic stores fail to be mobilised to the bone marrow; and that intravenous iron-dextran therapy, by-passing the intestinal mechanism for the regulation of iron absorption, carries a high risk of long-term hepatosplenic siderosis.