Iron Overload

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Iron Overload Objectives: -Definition -Causes of severe iron overload (>5g excess): 1.Increased iron absorption: - Hereditary (genetic, primary) haemochromatosis (GH) - Ineffective erythropoiesis 2. Increased iron intake 3. Repeated red cell transfusions -Classification of hereditary haemochromatosis: Types I, II, III, IV -Ineffective erythropoiesis -Increased iron intake

Iron Overload: 

Iron Overload Iron overload (excessive iron accumulation) occurs in disorders associated with excessive iron absorption or chronic blood transfusion, leading eventually to tissue damage. Excessive iron absorption Chronic blood transfusion Iron overload in parenchymal cells Iron overload in RE cells (liver, endocrine glands, heart) (macrophages in liver, spleen, BM)

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N.B. Hereditary Hyperferritinaemia: mutations of ferritin light chain gene → increased monoclonal serum ferritin→ ferritin deposition in eye → Cataract Syndrome with No tissue iron overload

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Clinical Features: Adult Only a small % of individuals with homozygous mutation present with clinical features. Chronic fatigue, hepatic disease (cirrhosis, HCC), endocrine disturbances e.g. pancreas, thyroid, parathyroid, arthropathy, melanin skin pigmentation In severe cases: heart failure or arrythmia Diagnosis: 1- Serum transferrin saturation: early indicator of parenchymal iron accumulation 2- Serum ferritin concentration: reflects increase iron turn over in RE cells 3- Confirmation: test for HFE mutation 4- Liver biopsy: assess liver damage. Done only if serum ferritin >1000 μg/L or liver enzymes 5- MRI : measures liver and cardiac iron

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Treatment: Regular venesection at 1-2 wks interval Aim: serum transferrin saturation <50%, serum ferritin concentration <50 μg/L Reversal of symptoms except cirrhosis and arthritis Types II and III: -Rare types Mutations in hemojuvelin, hepcidin or transferrin receptor 2 genes (AR) Both hepcidin (synthesis or secretion) Clinical Features: Children, adolescents or young adults Severe parenchymal iron overload with cardiomyopathy Type IV: - Rare type Mutations in ferroportin gene (AD) Liver biopsy: marked increase in RE iron, less parenchymal (hepatocyte) iron - NL serum transferrin saturation serum ferritin concentration

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Ineffective erythropoiesis: Inhibitory effect on hepcidin Increased iron intake: African siderosis; dietary intake of traditional beer which contains iron + genetic cause of increased iron absorption, mostly mutations in ferroportin gene.