Current Concepts in Liver Disease: An Update, Part 2
Moderator: Dr. Linda D. Ferrell
Section 5 -
Pathology of Hepatic Iron Overload
Vanderbilt University Medical Center
Nashville , TN
Iron overload is a commonly encountered problem in clinical practice and may be classified as primary
(genetic), acquired, or secondary to other inherited diseases, such as hereditary anemias. Dietary iron
is absorbed primarily by enterocytes in the duodenum, transported out of the intestine to the portal
blood stream where it is bound to apotransferrin, and transported to the liver. It is therefore not
surprising that excessive deposition of iron in liver is commonly encountered in liver biopsies, and
although there is broad overlap in the hepatopathology of iron overload, the pattern and degree of iron
deposition may suggest a specific diagnosis.
Genetic Conditions due to a Defect in a Gene Primarily Involved in Iron Homeostasis
- Primary Hereditary Hemochromatosis
- HFE-associated hereditary hemochromatosis (Type 1); autosomal recessive
- Non-HFE-associated hereditary hemochromatosis
- Juvenile hemochromatosis (Type 2); hepcidin or hemojuvelin mutations
- Transferrin receptor 2 mutations (Type 3)
- Ferroportin mutations (Type 4); autosomal dominant
- Chronic liver disease
- Chronic viral hepatitis (Hepatitis C and B)
- Non-alcoholic fatty liver disease
- Alcoholic liver disease
- Porphyria cutanea tarda
Blood Diseases Related to Iron Overload
- Hereditary spherocytosis
- Chronic hemolytic anemias
- Post-transfusional iron overload
Definition of Hemochromatosis
The term "hemochromatosis" was
originally used to describe iron accumulation not accounted for by other diseases and leading to organ
damage. However, recognition of mutations in the HFE gene as the basis for
most cases of hereditary hemochromatosis (HH) has led to a broader usage to include patients with
biochemical and genetic evidence for the disorder, without clinical manifestations. HH is now defined as
an autosomal recessive disorder of iron metabolism due to two mutant HFE
alleles. However, this definition does not account for conditions with an inherited hemochromatosis-like
phenotype without mutations in the HFE gene (non-HFE hemochromatosis), which account for roughly 10% of cases. 
Genetics of Hereditary (HFE) Hemochromatosis
HH due to HFE mutations is one of the most common genetic
disorders in Caucasians, with a prevalence of nearly 1 in 200. The two most common mutations are
designated C282Y (85-90% of affected individuals) and H63D, and account for ~85% of autosomal
recessive HH. The C282Y mutation prevents formation of a disulfide bond essential for binding of the
protein to β2-microglobulin and thus prevents transport of the HFE protein to the cell
surface. The H63D mutation affects binding of the HFE to the transferrin receptor and results in a less
severe phenotype; homozygosity for H63D mutation accounts for 2% or less of HH .
From 8 to 18% of northern, central, and western Europeans are heterozygotes for the C282Y mutation.
The high frequency of this mutation and data from population studies suggests origin from a common
ancestor in northwest Europe before 4000 BC . It is postulated that heterozygotes had a selective
advantage because increased dietary iron absorption was protective against iron deficiency. Selection
against homozygotes is minimal, because overt disease manifestations only develop after the reproductive
period is over .
Ferroportin disease is inherited in an autosomal dominant fashion . TfR2-associated hemochromatosis and most cases of juvenile hemochromatosis are
inherited as autosomal recessive disorders .
Many patients with HFE mutations are now identified at an
asymptomatic stage when hyperferritinemia is discovered upon routine testing. Individuals with HFE HH are asymptomatic until significant accumulation of iron occurs in liver and
other organs, a process which takes decades; men typically present in their 40s or 50s, with women
presenting a decade later because of the protective effects of menstruation. Skin pigmentation is less
frequently found with earlier diagnosis than in the past. Weakness, lethargy, abdominal pain, and
arthropathy are common non-specific presenting symptoms . In late stages, iron deposition in
pancreatic islets results in diabetes mellitus. Hypogonadism is very common. In young subjects, cardiac
manifestations may be the presenting feature, generally as a congestive cardiomyopathy, and may cause
death within a year of presentation if iron reduction is not instituted. Treatment is generally
phlebotomy to reduce iron stores.
Histopathology of the Liver in Iron Overload Disorders
In HH due to HFE mutations, iron is preferentially deposited in hepatocytes as granular,
refractile golden-brown hemosiderin. In early stages, this iron deposition is more prominent in zone 1,
but as the disease progresses, involves zone 2 and zone 3 hepatocytes. Inflammation is not a feature of
hemochromatosis, and fatty change is not specifically associated with the disorder. Iron also
accumulates in biliary epithelial cells.
The accumulation of iron causes necrosis of individual hepatocytes, releasing iron which
is taken up by Kupffer cells. In contrast to HFE HH, iron deposition in
ferroportin disease and hematologic disorders occurs preferentially in Kupffer cells, with involvement of
hepatocytes only when present in large quantities.
Fibrosis in HH occurs roughly when a threshold of ~15,000 micrograms iron/gram dry weight liver
is reached. It begins in periportal areas where iron deposition is greatest. Early cirrhosis is
typically micronodular and the liver is rust-colored. Risk for hepatocellular carcinoma may be up to 200
times that of the general population, and it is postulated that the presence of increased iron produces
oxidation stress that leads to p53 mutations. Of note, primary liver tumors arising in HH often displays
mixed hepatocellular/cholangiocarcinoma differentiation . Dysplastic nodules may contain relatively
little iron (iron free foci) compared to the rest of the liver.
Quantification of hepatic iron by histopathology is rarely indicated, but the following
semi-quantitative grading scheme  is helpful in surgical pathology practice:
1+ Fine granules in 5 to 10% of hepatocytes
2+ Fine granules in 10 to 50% of hepatocytes
3+ Fine and large granules in over 50% of cells
4+ Fine and coarse granules in nearly all hepatocytes
Quantitative analysis of iron in liver has long been the gold standard for diagnosis of HH
but is supplanted in some settings by genetic testing. HLA typing has been used as a surrogate test for
HH within kindreds because of the tight linkage between the HFE gene and the HLA complex, but has largely
been supplanted by testing for C282Y mutations.
Quantitative iron determination is used to determine the hepatic iron index by dividing
the weight of iron (micromoles per gram) in the biopsy by the patient's age in years. A level of >1.9
reliably distinguishes homozygosity for HH from the heterozygous state and alcoholic liver disease.
However, the hepatic iron index may exceed 1.9 in chronic hemolytic anemia, and levels < 1.9 are seen
in up to 15% of HH patients; in particular, its utility has not been established in the pediatric
population. The test may be performed on formalin-fixed, paraffin-embedded tissue or fresh tissue.
The differential diagnosis of HH primarily includes chronic liver diseases associated with
hepatic iron deposition, and hematologic disorders. Although iron overload from transfusions and/or
chronic hemolytic anemias is usually easily distinguished from HH by the preferential deposition of iron
in Kupffer cells rather than hepatocytes, a note of caution must be sounded here because of the recent
descriptions of the hepatopathology of ferroportin disease. Clinical history should aid in making these
distinctions, but in ambiguous cases, genetic testing may be indicated.
Hepatic iron overload is commonly seen in alcoholic liver disease and cirrhosis of any
type  and may overlap morphologically with HH. The pathogenesis of iron deposition in alcoholics is
largely unknown, but increased alcohol consumption may increase intestinal iron absorption in some
patients; heterozygosity for C282Y does not appear to influence hepatic iron levels or the risk of
fibrosis in these patients . Quantitative iron determination is usually helpful in distinguishing
these entities. Heavy alcohol consumption appears to accentuate the clinical expression of
hemochromatosis, greatly increasing the prevalence of cirrhosis .
Hepatic iron deposition in chronic viral hepatitis is typically modest, and is found
primarily in Kupffer cells; inconspicuous deposits in endothelial cells may also be noted. The
contribution of HFE heterozygosity and increased hepatic iron to non-alcoholic fatty liver disease is
controversial, with some but not all investigators reporting increased prevalence of HFE mutations in
Conversely, many patients with HH have histologic features of NASH . It should be
noted that HH by itself does not produce an inflammatory pattern of injury in the liver, and if present,
this should prompt consideration of superimposed disease processes or alternative diagnoses.
Primary Iron Overload Disorders
|Disorder ||Gene ||Protein Function ||Pathogenesis ||Clinical onset ||Population ||Liver Histopathology ||Main clinical manifestations|
|Hereditary hemochromatosis (Type 1) ||HFE ||Regulation of iron transport in intestinal crypt cells ||Excessive iron uptake from intestine ||40s & 50s ||Caucasians, mainly northern European ||Preferential deposition of iron in hepatocytes (periportal in early stages); spillover to Kupffer cells; fibrosis progressing to cirrhosis ||Liver disease; diabetes mellitus; cardiac disease; arthropathy; endocrine disease|
|Ferroportin disease (Type 4) ||SLC40A1 (solute carrier family 40) ||Iron export from cells (macrophages, intestine, placenta) ||Iron retention in macrophages ||40s & 50s ||Worldwide; many ethnic groups ||Preferential deposition of iron in Kupffer cells, with late spillover to hepatocytes; sinusoidal and periportal fibrosis ||Liver disease; mild anemia|
|TfR2-associated hemochromatosis (Type 3) ||TfR2 ||Uptake of iron-bound transferrin; may regulate hepcidin-HFE2 activity ||Unclear ||40s & 50s ||Rare; Italian, French, Portuguese, Japanese pedigrees ||Hepatocellular (periportal) iron accumulation; periportal fibrosis ||Liver disease; mild anemia; hypogonadism|
|Hepcidin-associated hemochromatosis and juvenile iron overload syndrome (Type 2) ||HAMP (hepcidin antimicrobial peptide); hemojuvelin HJV/1p21 ||Down-regulation of iron efflux from macrophages, intestine, placenta ||Excess iron release from macrophages results in influx into hepatocytes ||10s & 20s ||Diverse ethnic groups, mostly European; Greek, Italian, French, French-Canadian pedigrees ||Iron overload in hepatocytes, leading to fibrosis ||Endocrine and cardiac disease; liver disease is not a prominent feature|
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