transfusion iron overload
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Iron overload may develop in transfusion-dependent patients receiving red cells over a long period.

Iron overload is a major concern in patients with congenital and acquired anemias for whom regular transfusions are needed

  • under normal conditions, iron absorption and loss are balanced at approx1 mg/day. Transfused blood contains 200-250 mg of iron per unit
    • hence, patients with beta-thalassemia major (TM) or other refractory anemias receiving 2-4 units of blood per month have an annual intake of 5000-10 000 mg of iron or 0.3-0.6 mg/kg per day. The body has no mechanism for excreting this excess iron.
      • regular iron cell transfusions may increase this iron load by up to 10 g per year

Symptoms are similar to those seen in haemochromatosis with:

  • endocrine dysfunction - for example, diabetes mellitus
  • liver cirrhosis
  • cardiac failure
  • growth failure in children
  • delayed onset of puberty
  • skin pigmentation

Management:

  • serum ferritin to estimate body iron stores
  • desferrioxamine as a chelating agent, with vitamin C to enhance the therapeutic effect
    • iron overload may be prevented or treated with a chelating agent that complexes iron and allows excretion of chelator-iron complexes from the body. The most widely used chelating agent is desferrioxamine mesylate (desferrioxamine) administered subcutaneously or intravenously

Notes:

  • normal body stores are 3-4.0 g; daily losses are 1 mg
  • problems usually develop once more than 30 g of iron accumulate
  • each unit of red cells has 200 mg of iron
  • siderosis describes the deposition of iron in tissues
  • haemosiderosis describes the accumulation of excess haemosiderin
    • haemosiderin is an iron-storage complex. It is always found within cells and appears to be a complex of ferritin, denatured ferritin and other material
      • iron within deposits of hemosiderin is very poorly available to supply iron when needed. Hemosiderin can be identified histologically with "Prussian-blue" stain.
      • excessive accumulation of hemosiderin is usually detected within cells of the mononuclear phagocyte system (MPS) or occasionally within epithelial cells of liver and kidney.

Reference:

  • Kushner JP, Porter JP, Olivieri NF. Secondary iron overload. Hematology / the Education Program of the American Society of Hematology. American Society of Hematology. Education Program 2001;2001(1):47-61.
  • Hoffbrand AV et al. How I treat transfusional iron overload. Blood. 2012 Nov 1;120(18):3657-69.

 
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