Epidemiology and Disease Pathophysiology: Hereditary Haemochromatosis

1. Epidemiology and Disease Pathophysiology: Hereditary Haemochromatosis Pierre Brissot, MD Professor of Medicine Liver Disease Department University Hospital Pontchaillou Rennes, France

2. Overview • Definition/classification • Epidemiology • Prevalence • Penetrance • Inheritance • Pathophysiology • Iron overload • Hepcidin-ferroportin interaction • Ferroportin disease vs aceruloplasminaemia • Defect in hepcidin-ferroportin interaction • Diagnosis • Treatment • Family screening

3. Definition • Haemochromatosis = chronic iron overload of genetic origin1 • HFE-haemochromatosis (type 1) • Homozygous C282Y mutation (affected chromosome [6])1,2 • Non-HFE haemochromatosis

4. Non-HFE Haemochromatosis • Juvenile haemochromatosis (HC) (type 2)1 • Haemojuvelin mutations (type 2A) [1]*1,2 • Hepcidin mutations (type 2B) [19]*1,2 • TfR2 HC (type 3)1 • Transferrin receptor 2 mutations [7]* 1,2 • Ferroportin disease (Type 4)1 • Ferroportin mutations [2]* (subtypes A and B)1,2 • Aceruloplasminaemia3 • Ceruloplasmin mutations [3]*1,3 • Other types: atransferrinaemia, DMT1 mutation–related iron overload, GLRX5 mutation–related iron overload1,2 *Affected chromosome

5. Epidemiology—Prevalence • HFE-haemochromatosis (type 1)4 • >90% of cases1 • Generally of Northern European descent4 • Prevalence for C282Y homozygosity = 3/1000–5/10002,4 • Non–HFE-haemochromatosis1 • Rare (ferroportin disease) or exceptional

6. Epidemiology—Penetrance1Incomplete for HFE-HC–Phenotypic Variability (5-Scale Grading) 4 Life 3 Quality of life Quality of life 2 Ferritin Ferritin Ferritin 1 Tf Sat Tf Sat Tf Sat Tf Sat 0 CLINICAL PRECLINICAL Tf Sat (transferrin saturation) = >45%; ferritin = >300 µg/L (male), >200 µg/L (female). Quality of life symptoms = asthaenia, impotence, arthropathy; life-threatening symptoms =cirrhosis, diabetes, cardiomyopathy. Reprinted from Brissot P, et al, Hematology, Jan 2006:36, with permission from the American Society of Hematology.

7. Epidemiology—Penetrance1 Modifying factors • Acquired • Diet • Menses • Pregnancies • Blood loss/blood donation • Genetic • Polymorphism or mutations of other genes related to iron metabolism

8. Epidemiology—Inheritance1 Genetic transmission of HC • Autosomal recessive • Exception: ferroportin disease (Dominant transmission)

9. Pathophysiology5 Iron Overload Hepcidin Deficiency For Types 1, 2, and 3 HC HFE (type 1) or non-HFE (type 2 or 3) mutations 1 HFE or non-HFE mutations decrease hepcidin hepatic synthesis Hepcidin deficiency targets the duodenum, site of iron absorption As a result of 2, duodenalabsorption of iron increases Hepcidin deficiency targets thespleen As a result of 4, splenic iron release into the plasma increases As a result of 3 and 5, plasma iron concentration significantly increases Increased plasma iron (especially under its non–transferrin-bound iron species) produces parenchymal iron deposition (here, only the liver target is indicated) 1 Liver 2 HEPCIDIN 3 4 4 7 5 2 5 Spleen 6 IRON 7 6 Blood 3 Duodenum

10. Fe Fe Fe Fe Pathophysiology6 Physiology of Hepcidin-Ferroportin Interaction6 Cell 5 4 6 Ferroportin 3 1 Hepcidin Plasma 2 Ferroportin =iron export protein Circulating hepcidin Hepcidin bindsto ferroportin Internalization, then ferroportin degradation Degraded ferroportin Decreased iron release due to decreased ferroportin 2 3 4 5 1 6

11. Pathophysiology Quantitative Defect in Hepcidin-Ferroportin Interaction (Types 1, 2, 3 HC)7 Cell(= enterocyte and macrophage) Fe 3 Fe 4 5 2 Hepcidin Fe 1 Fe Fe Plasma Decreased circulating hepcidin Decreased hepcidin binding to ferroportin Internalization, but decreased ferroportin degradation Increased iron release due to increased ferroportin activity Increased ferroportin 2 3 4 5 1

12. Pathophysiology Iron Overload For Ferroportin Disease(type 4 HC) and Aceruloplasminaemia Deficiency of Cellular Iron Export Ferroportin Disease* Aceruloplasminaemia Transferrin Fe3+ 1 2 Cp 2 1 Fe2+ 3 4 Blood Blood . = Iron atom In both diseases plasma iron concentration is normal or low Mutated ferroportin 1 1 Mutated ceruloplasmin (Cp) Macrophagic iron excess due to deficient iron export (kupffer cell siderosis shown in 3) 2 Mutation leads to absence of ferroxidase activity (needed for iron uptake by transferrin) 2 Excessive ferroportin degradation leads to decreased cellular export of iron 3 *Valid for form A. In form B (resistance to hepcidin) mechanism of iron excess (corresponding to inactive hepcidin) is similar to type 1, 2, or 3 HC. 4 This leads to intracellular retention of iron

13. Fe Fe Pathophysiology Qualitative Defect in Hepcidin-Ferroportin Interaction (Type 4B HC) Hepcidin Resistance Cell(= enterocyte and macrophage) 4 3 Mutated ferroportin 5 2 Hepcidin Fe 1 Fe Fe Plasma Normal hepcidin Defect in hepcidin binding to ferroportin Decreased ferroportin degradation Increased iron release due to increased ferroportin activity Increased ferroportin 2 3 4 5 1

14. Diagnosis to Establish Iron Overload— Clinical and Biochemical • Clinical syndromes • Asthaenia, arthropathy, osteopaenia, skin pigmentation, impotence, diabetes, hepatomegaly, cardiac symptoms8 • Biochemical parameter • Hyperferritinaemia = >300 µg/L in men,>200 µg/L in women1 • Confounding factors1 • Alcoholism • Polymetabolic syndrome • Inflammation • Hepatitis Arthropathy Skin Pigmentation

15. Diagnosis to Establish Iron Overload—MRI9 • Magnetic resonance imaging (MRI) • Hyposignal (T2 weighted MRI) provides hepaticiron concentration • Benefits of MRI • Accurate, noninvasive strategy that most often eliminates the need for liver biopsy in diagnosingiron overload (www.radio.univ-rennes1.fr)

16. Diagnosis to Prove Genetic Origin1 • Family data • HC diagnosis or symptoms in favor of iron excess among family members • Personal data • Transferrin saturation level is a key parameter

17. Diagnosis to Prove Genetic Origin— Elevated TF1 Elevated transferrin (>60% men, >50% women) Caucasian ? Yes No Genetic test Genetic test C282Y/C282Y ? Haemojuvelin (Type 2A HC) Hepcidin (Type 2B HC) Ferroportin (Type 4B HC) TfR2 (Type 3 HC) if < 30 years old Yes No Type 1 HC

18. Diagnosis to Prove Genetic Origin— Normal or Low TF1 Normal or low transferrin (<45%) If anaemia & neurologic symptoms Plasma ceruloplasmin level Normal 0 (or low) Aceruloplasminaemia Genetic test Ferroportin? No Yes (Type 4A HC)

19. Treatment—Venesection Therapy • Treatment of choice for HC related to hepcidin deficiency (types 1, 2, and 3 HC) or inactivity (type 4B HC)4 • Revisited guidelines (for type 1 HC)1 • Start: grade 2 (ferritin level >300 µg/L for men, >200 µg/L for women)1 • Induction phase: 7 mL/kg body weight (<550 mL) weekly until ferritin = 50 µg/L1 • Maintenance phase: every 1–4 months until ferritin ≤50 µg/L (lifetime regimen thereafter)1

20. Results/Contraindications for Venesection Therapy1 • Results in types 1, 2, 3, and 4B • Good for asthaenia, skin pigmentation, liver disease, cardiac function • Moderate for arthropathy (which may worsen) and diabetes • Poor for cirrhosis (risk of hepatocellular carcinoma) • Ferroportin disease (type 4A HC) • Poorly tolerated: risk of anaemia • Aceruloplasminaemia • Contraindicated: anaemia Note: Life expectancy is normal if treatment starts before cirrhosis and insulin-dependent diabetes

21. Treatment Perspectives • Short-term perspective • Once daily oral chelator (deferasirox) • If ongoing study establishes good tolerance1 • Possibly for types 1, 2, 3, and 4A HC • Probably for type 4B • Mainly for aceruloplasminaemia • Longer-term perspective • Hepcidin supplementation (for types 1, 2, and 3 HC)

22. Family Screening1 • HFE-HC (type 1) • Whatever the grading of the C282Y/C282Y proband, should evaluate first-degree relatives (18 years or older) for C282Y mutation + serum iron markers (transferrin saturation, ferritin) C282Y = 2† C282Y = 0 or C282Y = 1* Grading No special follow-up Venesections if grade ≥ 2 *C282Y/wild-type †C282Y/C282Y

23. Family Screening1 • Types 2 and 3 HC (juvenile HC and TfR2 HC) • Similar procedure: search for identity using the proband mutation profile coupled with evaluation of individual’s biochemical iron status • Type 4 (A and B) HC (ferroportin disease) • The screening approach is different because of dominant transmission; hyperferritinaemia (corresponding to ferroportin mutation) would exist in 50% of siblings and offspring

24. Conclusions • In haemochromatosis, many new entities have been identified in addition to classic (type 1) haemochromatosis • These advances in knowledge of disease pathophysiology have improved diagnosis, and enhanced screening and approach to treatment of haemochromatosis

25. References Brissot P, de Bels F. Current approaches to the management of hemochromatosis. Hematology. Am Soc Hematol Educ Program. 2006:36-41. Pietrangelo A. Hereditary hemochromatosis—a new look at an old disease. N Engl J Med. 2004;350:2383-2397. Kono S, Suzuki H, Takahashi K, et al. Hepatic iron overload associated with a decreased serum ceruloplasmin level in a novel clinical type of aceruloplasminemia. Gastroenterology. 2006;131:240-245. Camaschella C. Understanding iron homeostasis through genetic analysis of hemochromatosis and related disorders. Blood. 2005;106:3710-3717. Loreal O, Haziza-Pigeon C, Troadec MB, et al. Hepcidin in iron metabolism. Curr Protein Pept Sci. 2005;6:279-291. Nemeth E, Tuttle MS, Powelson J, et al. Hepcidin regulates cellular iron efflux by binding to ferroportin and inducing its internalization. Science. 2004;306:2090-2093. Donovan A, Roy CN, Andrews NC. The ins and outs of homeostasis. Physiology. 2006;21:115-123. Brissot P, Le Lan C, Troadec MB, et al. Diagnosis and treatment of HFE-haemochromatosis. In: The Handbook: Disorders of Iron Homeostasis, Erythrocytes, Erythropoiesis. European School of Haematology (ESH); 2006: pp 454-464. Gandon Y, Olivié D, Guyader D, et al. Non-invasive assessment of hepatic iron stores by MRI. Lancet. 2004;363:357-362.

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