hereditary hemochromatosis - erin currin, md
TRANSCRIPT
Hereditary Hemochromatosis
Erin CurrinDecember 11, 2015
Faculty Sponsor: Dr. Richard
What is Iron? • Atomic Number = 26
o 26 electrons, 26 protons, 30 neutrons• Transition Metal• Ductile and Malleable• Conducts Heat and Electricity• Produces magnetic field• Makes up earths core entirely, mantle, crust• Oxidation-Reduction• Important in humans too!
Importance of Iron In Vivo
• Hemoglobino Part of porphyrin ring of heme moleculeo Each of the 4 globin subunit contains 1 iron atomo 2 million erythrocytes created per secondo Each mature erythrocyte: ~ 280 million molecules of hemoglobino Total Iron Flux: 2-3 x 1015 iron atoms/second
• Cytochrome p450• Myoglobin• DNA Synthesis• Mitochondrial function
Drakesmith et al, Cell Metabolsim, 2015; Rishi, Biosci Rep, 2015
Hemoglobin
Iron Redox• Readily undergoes oxidation-reduction reactions
o Ferric iron Fe3+ (oxidized) and ferrous Fe2+ (reduced)o Reduced form- most cytoplastmic irono Fenton Reaction: Donation of electron free radicals
o Free radicals: result in peroxidation of lipids, oxidative damage of DNA and macromolecules
Mackenzie, Antiox and Redox, 2008
Dietary Iron• Diet: the only source of iron • Normal diet: 10-20 mg per day• Normal absorption ~ 1-2 mg, in HH 8-10 mg• Main absorbable iron forms:
o Heme Iron: meat, fisho Non-heme iron: cocoa, lentils, spinach, etc.
• Vitamin C: Co-factor in non-heme iron absorption• Absorption site: Duodenum
o Via apical iron transporter DMT1 -divalent metal transporter 1o 5x more efficient for heme than non-heme irono ? Heme Carrier Protein (HCP1) – possibly low affinity heme- Fe
uptake
Yun, Crit Review in Onc/Heme, 2015; Cook Am J Clin Nutr, 2001; LeBlanc, Am J Cell Physiol, 2012
Duodenal Enterocyte
http://courses.washington.edu/conj/bess/iron/iron.htm; accessed Dec 2015
Iron Ins and Outs
• Total body iron ~ 3-4 gmo 2-3 gm erythrocytes o 1 gm hepatocyteso 2-3 mg in plasma, transferrin-bound
• Require~ 20-25 mg iron dailyo 80% erythropoiesis in the bone marrow ~ 20 mg
• Where does this come from?o 18-19 mg recycled: breakdown of hgb from senescent
RBCs by reticuloentdothelial macrophageso 1-2 mg absorbed by duodenal enterocytes (0.1%)
• Losses: Sloughing of enterocytes 1-2 mg, menses
Pietrangelo, NEJM, 2004; Yun, Crit Rev Onc, 2015; Brissot, Journal of Hepatology, 2015; Ganz, Biochemica, 2012
Pietrangelo, NEJM, 2004
Iron Transport in PlasmaTransferrin
• Absorbed by duodenum enters plasma• Not soluble in plasma (as a metal) • Binds Transferrin (Tf)
o 679 amino acid proteino Produced by hepatocyteso Tf binds 2 iron ions – ferric form-- reversiblyo Delivery to cells (ie: erytrhoid precursors in cells)o Tf-iron complex binds to Tf receptors (TfR1)o transferrin saturation (TS) of approximately 30%
Brissot, Journal of Hepatology, 2015; Keel, Exp Hematology, 2015s
Non‐Transferrin Bound IronLabile Plasma Iron
• Non-transferrin bound iron (NTBI): TS > 45%o Likely non-protein bound and protein boundo Targets parenchymal cellso Especially liver, pancreas, heart
• Labile Plasma Iron (LPI): TS > 75%o Generates ROSo Unregulated transport across cell membraneso May Downregulate of TfRo Redox active, chelatableo Permeates into organso Peroxidation of membrane lipids
Cabantchik, Best Practice & Research Haematology, 2005; Brissot, J Hepatol, 2015
Brissot, Biochima, 2012
NTBI/LPI in HH• Described in non-HH causes of IO• N=159 patients
o 23 patients with IO and HHo 24 patients with iron depleted HHo 33 alcoholic cirrhosiso 63 healthy controls
• NTBI/LPI higher in IO and HH• LPI correlated with abnormal LFTs• LPI present when TS > 75% regardless of cause
Le Lan, Blood 2005
Iron StorageFerritin
• Ferritin major storage molecule• Stores up to 4500 iron atoms• Iron stored as Ferric Iron Fe3+
• Protects cells from free radical damage• Downregulated in iron deficiency• Upregulated in iron overload• Main storage sites:
o Livero Reticuloendothelial cells (macrophage, monocytes)
• Mean Value:o Men 12-300 ng/ml; women 12-150 ng/ml
Brissot, Journal of Hepatology, 2015; Hentz, Cell, 2004 ; Yun, Crit reviews in Onc/Heme, 2015; Medline 2015
Iron ExportFerroportin
• Multidomain transmembrane protein • Encoded by SLC40A1• Sole Iron Exporter
o Basolateral membrane of duodenal enterocyteo Plasma membrane of macrophage (splenic, hepatic)o Hepatocytes, Placental Syncytiotrophoblastso Lung, renal tubules, erythrocyte precursors
• Ferrportin in iron deficiencyo Enhances iron export into plasma
• Regulated by the protein hepcidin
Ganz, Hematology, 2011; Ganz, Biochemica, 2012; Pietrangelo, Gastroenterology, 2015; Cianetti, Advances in Hematology, 2010
Regulator of Ferroportin: Hepcidin
• Hepcidin 25 amino acid protein• Mainly produced by hepatocytes• Major regulator of plasma iron• Encoded by HAMP• Function:
o Hepcidin binds to ferroportino Internalization and destruction of ferroportino Decreases cellular iron export o Inhibits dietary absorption, macrophage iron recycling
• … what controls hepcidin?Ganz, Hematology, 2011; Bissot, Journal of Hepatology, 2015
Hepcidin‐FerroportinSystem
Rishi, Blood, 2015
HepcidinRegulation
Regulators of Hepcidin1) Inflammation/Infection
o Inflammatory signals, ie: IL-6 by monocytes/macrophages via TLRs during infection
o TNF alpha, IFN gammao Lipopolysaccharide (LPS)
2) Hypoxiao Hypoxic conditions may decrease production of HAMP
Nicolas, J Clin Invest, 2002; Rishi,Biosci, 2015
Regulators of Hepcidincont.
3) Erythroid Regulators: Several potential regulators• Discovery of hormone erythroferone (EFRE)
o Thought to meditate hepcidin during stress hematopoiesis• EFRE knockout mice failed to suppress hepcidin• Delayed recovery from hemorrhage
o Mice with thalessemia intermedia– increase EFRE• May contributes to suppression of hepcidin
o Uncertain role in homeostasis
• TFRCo TFEC peak level on proerythroblastso TFRC expression on erythroids may suppress hepcidino Via soluble factor Xo TFR1 may increase ERFE expression
Kautz et al, Nature Genetics, 2014; Koury, The Hematologist, 2015l Keel Exp Hematology, 2015
Regulators of Hepcidincont.
4) Iron StoresHFE gene: modulator of hepcidin
• Feder et al, 1996 Identified a MHC Class 1 like gene, HFE• Does not participate in antigen presentation• Mutated in HH
• 343 amino acid protein• 3 extracellular domains
Barton et al, Gene, 2015; Feder et al, 1996,
HFE Mutations3 missense mutations: missense
1) C282Y • Tyrosine replace
cysteine at position 2822) H63D
• Aspartic acid replaces histadine at position 63
3) S65C (later discovery)• Cysteine replace serine
at position 65Mutations result in decreased hepcidin
Feder, Nature, 1996; Mura, Blood, 1999
S65C
How does HFE regulate Hepcidin?
• HFE thought to complex with TFRCo Transgenic induction of hepcidin without TFRC
• BMP (bone morphogenic protein) pathway in livero Activated BMP-1 receptors phosphorylate SMAD proteinso In turn, induce hepcidin transcription
• Wu et al, 2014• Wild type HFE binds to BMP -1 Receptor “Alk 3”
o Cultured hepatocytes and mouse livero HFE increase Alk 3 expression on cell surfaceo Activates BMP/SMAD signaling hepcidin transcription
Wu, Blood, 2014; Muckenthaler, Blood, 2014
Muckenthaler, Blood, 2014
HFEmutations and hepcidin
• C282Y and H63D • Mutations fail to increase Alk3 on cell surface• Impairment of BMP mediated activation pathway• Mechanisms differ:
o Speculated that HFE C282Y does not reach the cell surface • Sequesters Alk3 within the cell
o H63D failed to inhibit ubiquitination of ALK3• Further work needed
HFE Hereditary Hemochromatosis
HemochromatosisHistory
• Recognized in 1880so Diabetes, bronze skin and cirrhosiso 1889: Term Hemochromatosis for bronze stained organs
• 1935: disease recognized as inheritedo Metabolic defect causing excess iron in tissues
• 1970s-80s: autosomal recessiveo Short arm of chromosome 6, encoding HLA-A*3
• 1996: “hemochromatosis gene” (HFE) identified• C282Y• H63D
Pietrangelo, NEJM, 2004Simon, Pawlotsky, et al, Nouv Presse Med, 1975; Simon, Le Mignon et al, Am J Hum Genet 1987
Pathology Education Informational Resource (PEIR) Digital Library
HFE: Many new mutations discovered
Barton et al, Gene, 2015
Types of HHType Pathogeneic Mutations Mutation
FrequencyOnset < 30 years
1) Classical HFE: C282Y, H63D, S65C, others C282Y, H63D Common
AR Uncommon,
2) Non Classical “Juvenile”
2A: mutations in HAMP 2B: HJV Hemojuvelin *
Rare AR Common
3) NonClassical
TFR-2 Transferrin Receptor Protein 2
Rare AR Common
4) Non Classical“FerroportinDisease”
SLC40A1Ferroportin
Q248Hcommon in SubsaharanAfrica
AD Uncommon
Crownover, AFP, 2013; Zanella, Blood, 2015; Pietrangelo, NEJM, 2004
AR= autosomal recessive, AD = autosomal dominan* HJV: binds to BMP proteins
C282Y Prevalence• Most common form of HH: 80-85% patients• Arise from Celtic/Viking ancestor ~ 4000 years ago• Does not affect reproduction• Protective? • Mean allelic frequency ~ 6% Caucasians• C282Y homozygosity in Caucasians: 1:200-300
o Geographic variation, migrationo As high as 1:83 Irelando 10x more common than CF dF508 gene
• H63D mean allelic frequency 14% Caucasians
Pietrangelo, Gastroenterology, 2015; Adams PC, Lancet, 2007; Bacon, Hepatology, 2011
Single Allele FrequencyC282Y H63D
Distante, Human Gen, 2004
Prevalence of C282Y 30, 672 caucasian subjects Kaiser Permanante, CA
Heterozygous0.937 %
Homozygous0.062%
Beutler, Blood, 2003
Genotypic and Phenotypic Profiles
• n=123, referred for elevated TS, asymptomatic• Genotyped, phlebotomy to iron depletion• mobilized Iron quantified (gm Iron = hct/3x wt of blood x .0035)
Sham et al, Blood, 2000
Varied Iron Loading
Waalen, Best Practice & Research Clin Haem, 2005
Normal Ferritin in C282Y homozygotes
Bacon, AASLD, Hepatology, 2011
HealthIron Study
• N=31,192 persons N. European/Australian descent• age 40-69, prospective• 203 patients with HH, followed avg 12 years• Cirrhosis, fibrosis, HCC, abnormal LFTs, 2-3rd MCPs• 28.4% Men, 1.2% women• Ferritin > 1000ug/L more cirrhosis, more symptoms• Arthropathy unrelated to ferritin levels
Allen, NEJM, 2008
ScreeningRecommendations
• Per AASLD practice guidelines:o Patients with suggestive symptomso Characteristic physical findingso Family Historyo All first degree relatives of HH patient
Bacon, Hepatology, 2011
ScreeningRecommendations
• Approach to Diagnosis: Who should get gene testing?o If TS >45% (serum iron/TIBC X 100)
• ~ 45% high sensitivity for detecting C282Y homozygotes• Lower specificity /PPV picks up mild iron overload
o ferritin > normal • 200 women mcg/dl, 300 men ug/L mcg/dl• No difference fasting vs. not fasting• Less biologic variability than TS• High false positive
o If both abnormal, order HFE gene testing
Population Studies• Hemochromatosis and Iron Overload Study (HEIRS)
99,711 North Americanso 88% men C282Y/C282Y had Ferritin >300 ug/L o 57% women C282Y/C282Y Ferritin > 200 Ug/L
• Kaiser Permanente Studyo 77% men C282Y/C282Y Ferritin >250 ug/Lo 56% women C282Y/C282Y Ferritin > 200 ug/L
• Study in Individuals <35 yearso TS <45% and normal ferritin NPV 97%
Bacon, Hepatology, 2011; Beutler, Blood, 2002; Adams, NEJM, 2005
Clinical Manifestations
Disease Presentation before Gene testing
• Symptoms BEFORE era of screening: o Weakness, Lethargyo Abdominal Paino Impotenceo Cardiac Failure
• Physical Findings BEFORE era of screening:o Cirrhosis/HCCo Hepatomegalyo Gynecomastiao Testicular Atrophyo Skin pigmentationo Diabeteso Arthropathy 2nd-3rd MCP
• Classic Triad DM, Cirrhosis, Skin findings > 20 gm Iron
Bacon, Gastroenterology, 2011
Disease Stages in gene testing era
European Assoc Study of Liver Disease Consensus:Stage 1: Refers to patients with genetic disorder with no increase in iron stores who have a genetic susceptibilityStage 2: patients with genetic disorder who have phenotypic evidence of iron overload without tissue or organ damageStage 3: genetic disorder with iron overload and iron deposition with tissue and organ damage occurs
Bacon, Hepatology, 2011; Allen, NEJM, 2008
Bacon, Hepatology, 2011
Liver Manifestations• Excess iron deposition in liver, hepatocytes• Fibrosis, Cirrhosis: ferritin > 1000 ng/ml• HCC develops ~ 8-10% patients with HH
o Cirrhosis almost always presento RR 20, annual risk 3-4% incidence if cirrhosiso Follow guidelines for advanced fibrosis/cirrhosis
• HCC Surveillance if cirrhosiso Every 6 month US, gold standardo Sensitivity 94%
Kew, Liver Cancer, 2014; Crownover, AFP, 2013; Colombo, Uptodate Prevention HCC, 2015
Disease Modifiers
Pietrangelo, Gastroenterology, 2015; Bacon, Hepatology, 2011; Fletcher, Gastroenterology, 2002; Tayrac, J Hepatol, 2015
• ALCOHOL• Australian C282Y/C282Y > 60 gm /day ETOH
o 60% cirrhosis vs. < 7% no alcoholo Alcohol induce hepatic fibrogenesis and oxidative stress
• NAFLD/NASH• Hepatitis B, C• Genetic, Polymorphisms in genes
o FPN, MP, Tf, TFR2, ARNTL, GNPATo Genome Wide Association Study
Rs2811647 Tf polymorphism increased Tf and serum Iron• Male
Cirrhosis rates in HH
Assessment Intrahepatic Iron
• Gold standard-Liver biopsyo Measurement of hepatic Iron concentration (HIC)o > 80 micromoles/gm of dry weighto Hepatic Index > 1.9 mol/kg/yr (HIC/age yrs)o Invasive
• Meta-Analysis of MRI for identifying Iron Overloado 20 studieso Identified patients without iron overload
• Negative LLR 0.10, 0.05o Less accurate for definite diagnosis of iron overload
• Positive LLR 8.85, 4.86
Sarigianni, et al, Clinical Gast and Hep, 2015; Bacon, Clin Gast and Hep, 2015
Liver Imaging• T2* MRI - relaxometry method-weighted MRI
o Very quick, single breath holdo Approximation of stored irono Correlates with iron loadingo Limitations with calibration (only at 1.5T)
• Dynamic elastrography:o Surrogate for fibrosis evaluationo assessment of propagation of shear waves within tissues to
calculate visco-elastic propertieso First Generation: Transient elastrography (FibroScan)o Second Generation: ARF (acoustic radiation force) o Used widely in Europe
Van Beers, Journal of Hepatology, 2015; St. Pierre, Magn Reason Med, 2014; Knovich, Blood Rev, 2009
FibroScan
Cardiac Manifestations• Usually occurs after significant hepatic iron uptake• Clinical Features:
o Early restrictive cardiomyopathy, diastolic dysfunctiono Progress to end stage dilated cardiomyopathyo Biventricular heart failureo Predisposition to arrhythmias, conduction system, AV block
• Diagnosis:o Biopsy- INVASIVE! o ECHO- can determine cardiac functiono Cardiac MRI: T2* MRI
• if < 20 ms, correlate with cardiac iron loading
Bejar, Clin Med Insights: Cardiology, 2015; Murphy, Journal of Cardiac Failure, 2010
Joint Manifestations• Most common affected joints:
o 2nd/3rd MCPo Wrists, hip, ankleso Worse in women
• Presentation:o OA like symptoms, pseudogout, synovitis resembling RAo Chondrocalcinosis of wrist/knee up to 50% patientso High risk severe large joint requiring joint replacement
• Radiographso Joint space narrowing, subchondral cysts, osteophytes
• Treatmento Often not improved by phlebotomy
Husar‐Memmer, Curr Rheumatol Rep, 2014; Adams, Blood, 2010
Husar‐Memmer, Curr Rheumatol Rep, 2014
Other Manifestations• DM
o Occurs late in diseaseo Most patients with DM already have cirrhosis
• Hypopituitarismo Iron deposition in pituitary cells – anterior > posterioro Decreased levels of trophic hormones
• Testicular Atrophyo Secondary from pituitary insufficiencyo Less commonly testicular iron deposition
• Skin pigmentation
Treatment
Treatment: Phlebotomy• Treatment of choice for HH: Phlebotomy• No randomized trial• Starting phlebotomy before cirrhosis/DM
o Goal: prevention of end organ damageo Large population based studies show decreased survival in
untreated HH patients• One unit of blood: 200-250 mg iron
o When IO severe, > 30 gm, ~ 2-3 years to removeo Check hct/hgb prior to phlebotomyo Avoid l < 80% starting hcto Ferritin falls faster iron mobilization, reflects depleted storeso TS can remain elevated until stores are depleted
Bacon, Hepatology, 2015; Adams, Blood, 2010; Adams, Gastroenterology, 1991
Treatment Algorithm
Adams, Blood, 2010
Treatment and Maintenance
• Goal: Serum Ferritin of 50 ug/L or lesso Some practitioners and patients may target ~ 20-30 ug/Lo SF preferred over TS o TS may remain high when body iron stores when SF lowo Targeting TS may result in iron deficiency, fatigue
• Rate of re-accumulation o Wide variationo Some require monthly maintenance, others 1-2x/yearo Others may go yearso Check SF every 6 months, personalized maintenance plan
Phlebotomy‐ increase Iron absorption?
• Lynch et al, Blood, 1989• Measured iron absorption from test meals in HH
Serum Ferritin Non Heme Iron Absorption
Heme Iron Absorption
Untreated: SF>1000 ug/L
9% 41%
Partially treatedSF ~ 538 ug/L
12% 50%
Fully TreatedSF ~ 14 ug/L
42% 39%
Lynch, Blood, 1989, Adams, Blood, 2010;
Reversal of liver damage• Falize et al, 2006• 36 patients with C282Y/C282Y
o 13 patients with Grade 3 fibrosis, 23 patients with Grade 4 o 2 biopsies, lag time of 2 years, treatment with phlebotomyo Mean follow up of 9.7 yearso Fibrosis regression correlated with compliance to therapy
69%35%
Reversal of other end‐organ damage
• Cardiac:o LV dysfunction improved with phlebotomyo Dilated cardiomyopathy likely not reversedo Fluid shifts with phlebotomy maybe challenging with CHF
• Diabeteso Improved glucose control, DM usually not reversed
• Skino decreased pigmentation
• Livero Reduction in LFTso Fibrosis can be reversedo Reduction in HCC risk if iron removed before cirrhosis
• Testicular Atrophyo No reversal
Intolerance of Phlebotomy• Bone marrow unable to recover• End organ damage, ie: CHF, unable to tolerate
volume shifts, no IV access• Options
o Erythrocytapheresiso Chelating agents
• Deferoxamine• Deferasirox
Therapeutic Erythrocytapharesis
• Therapeutic Erythrocytopharesis (TE)• Removes iron as hemoglobin
o must have no or mild anemiao must have sufficient rate of effective erythropoiesis
• Isovolemic, large volume TE removes more blood per session than phlebotomyo Spares plasma proteins, coagulation factors, proteinso May achieve iron depletion more quicklyo More costly than phlebotomy
• Side effects: o transient hypovolemia, monitor iron levels closely
• Rarely used
Adams, Blood, 2010
Deferoxamine• Desferal• Subcutaneous Infusion• Urine as chelate• Most experience in non-HH patients• Small case series, DFO as effective as phlebotomy
500 ml/weekly in removing irono Cardiomyopathy improved in 1 patient
• Compliance- fair• Expensive• Side Effects: infusion site reactions, hearing, vision,
growth, skeletal abnormalities, zinc deficiency, Yersinia infection, renal effects
Nielsen, British Journal of Hematology, 2003; Adams, Blood, 2010
Deferasirox• Exjade• Oral• Stool as chelate• Phase 1/2 Dose escalation Trial, 48 week (2010)
o C282Y/C282Y; SF 200-3000 ng/ml, TS > 45%, no cirrhosis, n=49o Starting dose of 5 mg/kg; 10 mg/kg; 15 mg/kgo Side effects dose dependento LFTs abnormalities (6) and increased Cr (8)o Diarrhea, nausea, abdominal paino Mean SF decrease after 48 weeks respectively: 63%, 74%, 74% o Dose of 10 mg/kg/day appears safest
• SE: renal failure, hepatic failure, GI hemorrhage• Expensive
Adams, Blood, 2010; Phatak, Hepatology, 2010
Other Therapeutic Options
• Deferiprone (Ferriprox)o Could not find data for use in HFE HH
• Proton Pump Inhibitors:o Reduced absorption of non-heme iron in test meal (7 patients)
• Insufficient data to make recommendation
Hutchinson, Gut, 2007; Adams, Blood, 2010
Before PPI
After PPI for 7 day
Dietary Management
• Black tea inhibits absorption non-heme iron• Vibrio Vulnificans– warm coastal waters, GN Bacillus
Adams, Blood, 2010