Hemochromatosis

Diagnosis

Indications for Testing

• Diagnostic confirmation of hereditary hemochromatosis (HH) in an individual with biochemical or clinical findings of iron overload
• Screening for adult family members of individuals with a C282Y/C282Y or C282Y/H63D genotype
• Carrier testing for the reproductive partner of an individual with HH

Laboratory Testing

•  Fasting serum transferrin saturation (STS) – calculated from serum iron and iron binding capacity
  • Fasting STS
    • Using a saturation cutoff of 45% is more sensitive for detecting mild disease, but also identifies heterozygotes not at risk for developing clinical findings
  • Elevated serum ferritin (SF)
    • Increases progressively over time in individuals with untreated HFE-caused HH
    • SF is an acute phase reactant – elevated concentration alone is not specific for iron overload because increased levels may also be caused by inflammatory or neoplastic disorders
• C282Y and H63D genotyping
  • Heterozygosity for the common HFE mutations C282Y, H63D, or S65C
    • May  be associated with elevated serum iron levels but not with clinical symptoms of HH (unless an additional rare, undetected HFE mutation is present)
    • Consider HFE full gene sequencing and possibly deletion/duplication analysis
  • Homozygosity for the C282Y mutation or compound heterozygosity for C282Y/H63D in individuals with clinical and biochemical evidence of iron overload
    • Confirms diagnosis of HH
    • Only minority develop clinical symptoms of HH
  • Homozygosity for the C282Y mutation in individuals without clinical and biochemical evidence of iron overload
    • High risk for iron overload
    • Only minority develop clinical symptoms of HH
  • Compound heterozygosity for C282Y/H63D in individuals without clinical and biochemical evidence of iron overload
    • Moderate risk for iron overload
    • <2%  risk for developing clinical symptoms of HH

Other Testing

• Quantitative phlebotomy
  • Use to determine quantity of iron that can be mobilized
  • Confirms diagnosis of HFE-HH in individuals with hemochromatosis and  no diagnostic genotype who are unwilling to undergo liver biopsy
    • Affected persons can mobilize at least 4 grams of iron

Histology

• Liver biopsy – useful in confirming hepatic iron overload, particularly in individuals with hemochromatosis and no common HFE mutations
  • Testing should include
    • Measurement of hepatic iron concentration
    • Calculation of hepatic iron index and stains to assess pattern and severity of iron overload
      • Index >1.9 suggests hemochromatosis
    • Stains to determine the presence or absence of hepatitis and fibrosis – hepatitis B surface and core antigen, Alpha-1-Antitrypsin (AAT)

Imaging Studies

• Quantitative MRI – may be used as an alternative to liver biopsy
  • Requires expertise with validation

Differential Diagnosis

• Other inherited forms of  hemochromatosis (non-HFE)
  • Type 2B – juvenile hemochromatosis (HJV, HAMP variants)
  • Type 3 – transferrin receptor 2 mutation (TFR2)
  • Type 4 – ferroportin disease (SLC4OA1)
  • Neonatal hemochromatosis
• Secondary iron overload
  • Iron loading anemias (eg, thalassemia)
  • Transfusion iron overload
• Chronic liver disease 
  • Alcoholic siderosis
  • Porphyria cutanea tarda
  • Portocaval shunt
  • Alcoholic liver disease
  • Hepatitis
• Other
  • Aceruloplasminemia
  • Sub-Saharan African iron overload

Screening

Monitoring

Clinical Background

Hemochromatosis is an iron overload disorder caused by excess iron being stored in the body that can be inherited or acquired. Hereditary hemochromatosis (HH) is a genetic disorder resulting in excessive absorption and storage of dietary iron, leading to progressive iron accumulation in tissues and resulting in organ damage.

Epidemiology

• Incidence – allele frequency varies by ethnicity; most common in Caucasians of Northern European descent
• Age – peaks in 40s-50s
• Sex –  M>F, 2:1
• Ethnicity – Caucasian

Inheritance

• Autosomal recessive
  • HJV (HFE2) gene – encodes for hemojuvelin; 90% of reported cases
  • HAMP (HEPC) gene – encodes for hepcidin; <10% of reported cases
• Mutations of the HFE gene are responsible for the most common form of HH (HFE-HH)
  • Common HFE mutations, prevalence, and carrier frequency
    • C282Y
      • Homozygosity – 85% of cases
      • Variable penetrance – most patients will have biochemical abnormalities; up to 2% will have characteristic clinical endpoints
      • Severe disease
      • 11% carrier frequency in Caucasians
    • H63D
      • Homozygosity – 1% of cases
      • Compound heterozygosity (C282Y/H63D) – 5% of cases
      • Mild disease
      • 25% carrier frequency in Caucasians
    • S65C
      • Effect unknown
      • 1% carrier frequency in Caucasians
  • Heterozygosity for C282Y, H63D, or S65C does not cause HH
  • Penetrance for C282Y homozygosity – high for biochemical abnormalities but may be as low as 2% for characteristic clinical endpoints

Pathophysiology

• Pathogenesis
  • High rate of iron absorption across duodenal enterocytes
  • Increased iron stores of ferritin – most found in reticuloendothelial macrophages with limited excretion
  • Eventual deposition of excess iron in other organs, causing tissue damage
• First biochemical manifestation is increased transferrin saturation due to the following
  • Uncontrolled influx of iron from enterocytes and macrophages
  • Inadequate synthesis of the hepatic iron-regulating hormone, hepcidin

Clinical Presentation

• Classic HH – effects of excess iron are cumulative;
  • Severe disease rarely occurs in individuals <35 years
• Subtle, nonspecific symptoms prior to clinical diagnosis
  • Fatigue, weakness
  • Progressive increase in skin pigmentation
  • Loss of libido
  • Arthralgias
• Hepatic disease
  • Liver function abnormalities – >95% of patients
  • Chronic abdominal pain
  • Hepatomegaly
  • Cirrhosis
  • Hepatocellular carcinoma – 200-fold increase compared to cirrhotic patients with chronic viral hepatitis B or hepatitis C
• Cardiovascular disease
  • Cardiomyopathy – dilated, restrictive or mixed
  • Arrhythmias – atrial tachycardias most common
• Endocrine disease
  • Diabetes – deposition in pancreas
  • Thyroid dysfunction – iron deposition with fibrosis
  • Hypogonadism, infertility – iron deposition in the pituitary; relatively rare
• Skeletal disease
  • Arthritis – metacarpophalangeal joint; second and third joint
  • Dermatologic disease – melanoderma; relatively rare
    • Bronzing, gray, or brown discoloration – increased melanin production and iron deposition in skin
    • Not usually truncal in distribution

Treatment

• Phlebotomy – first and preferred method of ferritin control
  • Clearly indicated only when clinical symptoms are present
  • Therapeutic phlebotomy until hematocrit is 75% of baseline
  • Goal – reduce serum ferritin to approximately 50 μg/L
• Iron chelation therapy
  • Useful for patients who cannot have phlebotomy

Pediatrics

Clinical Background

Epidemiology

• Prevalence – rare
• Age – 10-30 years (for diagnosis)
• Sex – M:F, equal

Inheritance

• See Clinical Background tab

Clinical Presentation

• Earlier onset – typically <30 years
  • More severe disease than adult forms
• Typical presentation – cardiomyopathy and hypogonadotropic hypogonadism
• Other organ involvement similar to adult onset – cirrhosis, diabetes mellitus, arthritis, increased skin pigmentation

Diagnosis

Indications for Testing

• Arthralgias, skin pigmentation, diabetes

Laboratory Testing

• Serum ferritin (SF) – ranges from 1,000-6,000 μg/L
• Fasting serum transferrin saturation (STS) – ≥45% suggests further testing necessary
  • Normal value in children is 15-50%
• HJV, HAMP genotyping

Histology

• Liver biopsy
  • Hepatic iron index – >1.9 suggestive of disease
  • Iron index not applicable to children <14 years
  • Utility of hepatic iron quantitation in a child is controversial

Imaging Studies

• MRI may be used to quantify hepatic iron load

Differential Diagnosis

• Other inherited forms of  hemochromatosis (non-HFE)
  • Type 2B – juvenile hemochromatosis (HJV, HAMP variants)
  • Type 3 – transferrin receptor 2 mutation (TFR2)
  • Type 4 – ferroportin disease (SLC4OA1)
  • Neonatal hemochromatosis
• Secondary iron overload
  • Iron loading anemias (eg, thalassemia)
• Chronic liver disease 
  • Porphyria cutanea tarda
• Other
  • Aceruloplasminemia
  • Sub-Saharan African iron overload

Monitoring

• Refer to Monitoring tab

Indications for Laboratory Testing

• Tests generally appear in the order most useful for common clinical situations
• Click on number for test-specific information in the ARUP Laboratory Test Directory

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Iron, Plasma or Serum 0020037 Method: Quantitative Spectrophotometry	Can be used to estimate STS Order with serum transferrin
Transferrin, Serum 0050570 Method: Quantitative Immunoturbidimetry	Can be used to estimate STS Order with iron (plasma or serum) To determine serum transferrin saturation when ordering both serum transferrin and plasma or serum iron tests, the following equation is necessary for interpreting test results STS (%) = (100 x serum iron)/TIBC
Aspartate Aminotransferase, Serum or Plasma 0020007 Method: Quantitative Enzymatic	Monitor treatment of hemochromatosis

Diagnostic Algorithm

  Hemochromatosis Testing Algorithm