Iron

Iron may be considered a trace element if the large amounts present in haemoglobin are discounted. The recommended daily intake is 10-15 mg per day, of which only 1-2 mg is absorbed. The main transport protein for iron is transferrin, which is synthesised in the liver at a rate inversely proportional to body stores. Ferritin is an iron storage protein found in most cells of the body, particularly the liver, and provides a readily available reserve. Haemosiderin is an insoluble aggregate protein also found primarily in the liver during excessive storage and from which iron is less readily available.

Iron deficiency is one of the most prevalent disorders, even in developed countries. It may either be due to inadequate dietary intake or chronic blood loss. Acute iron toxicity from overdosage of inorganic iron tablets is the commonest acute poisoning in children. Chronic iron overload may arise from genetic haemochromatosis in which there is excessive iron absorption or secondary to repeated transfusions (transfusion siderosis in sickle cell disease or thalassaemia), or to alcoholic liver disease. Genetic haemochromatosis is due to mutations in the HFE gene (C282Y and H63D) and is primarily found in Caucasians.

Neonatal haemochromatosis is a rare, but particularly severe cause of iron overload and is unrelated to the adult form. Liver transplantation within the first few weeks of life is required for survival.

A raised transferrin saturation (> 65%) is strongly suggestive of haemochromatosis. Until recently, diagnosis was usually confirmed by hepatic iron measurements, but today molecular techniques for identification of the above mutations is more common and less invasive. Treatment of transfusion siderosis is with the iron chelator desferrioxamine. Measurement of urinary iron excretion during chelation therapy can help optimise the dosage.