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
    •  HFE genotyping should only be performed among individuals with iron overload (eg, elevated fasting transferrin saturation >45%) or a known family history of HFE-associated hereditary hemochromatosis (Choosing Wisely: 5 Things Physicians and Patients Should Question, 2015; American College of Medical Genetics and Genomics
    • 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, mostly in individuals with hemochromatosis and absence of 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 
  • Other
    • Aceruloplasminemia
    • Sub-Saharan African iron overload

Screening

  • Screen with fasting serum transferrin saturation (calculated from serum iron and iron binding capacity) and serum ferritin
  • U.S. Preventive Services Task Force does not recommend widespread screening
  • American College of Physicians (ACP) recommendation – offer testing to the following
    • Adult Caucasian men of North European ancestry >25 years
    • First-degree relatives of patients with disease
  • American Association for the Study of Liver Diseases recommendation – offer testing to the following
    • All patients with evidence of liver disease without obvious etiology
    • First-degree relatives of patients with disease

Monitoring

  • Depletion phase – hemoglobin/hematocrit, mean corpuscular volume (MCV), serum ferritin until ferritin <50 μg/L
    • If hematocrit drops >20% of initial level, next phlebotomy should be postponed
  • Maintenance phase – check ferritin every 6 months to maintain <50 μg/L
  • Do not base frequency of phlebotomy on transferrin concentration

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(~1/200-400)
  • Age – peaks in 40s-50s
  • Sex –  M>F, 2:1

Inheritance

  • Types of HH and genes involved

    Types of HH and Genes Involved

    Type

    Gene

    Inheritance

    Protein

    Onset

    Phenotype

    1

    HFE

    AR

    HFE

    Adult

    Moderate

    2 A

    HJV

    AR

    Hemojuvelin

    Child

    Severe

    2 B

    HAMP

    AR

    Hepcidin

    Child

    Severe

    3

    TFR2

    AR

    Transferrin receptor

    Young adult

    Moderate

    4

    SLC40A1

    AD

    Ferroportin

    Adult

    Moderate

    AR – autosomal recessive; AD – autosomal dominant

    Source: Zarrilli, et al, 2013

  • Mutations of the HFE gene are responsible for the most common form of HH (HFE-HH)
  • Common HFE mutations

    Common HFE Mutations

    Mutation

    Homozygosity

    Carrier frequency

    Type of disease

    Heterozygosity

    C282Y

    85% of cases

    • Variable penetrance
    • Most patients have biochemical abnormalities
    • Up to 2% have characteristic clinical endpoints

    11% in Caucasians

    Severe

    C282Y – does not cause HH

    Compound C282Y/H63D heteroxygosity – 5% of cases

    H63D

    1% of cases

    25% in Caucasians

    Mild

    H63D – does not cause HH

    Compound H63D/C282Y heterozygosity – 5% of cases

    S65C

     

    1% in Caucasians

    Unknown

    Does not cause HH

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

  • Tissue and organ damage typically appear after age 30
  • Classic HH – effects of excess iron are cumulative;
    • Severe disease rarely occurs in individuals <35 years
  • Subtle, nonspecific symptoms prior to clinical diagnosis
    • Fatigue, lethargy
    • Progressive increase in skin pigmentation
    • Loss of libido
    • Arthralgias
  • Hepatic disease
  • Cardiovascular disease
    • Cardiomyopathy – dilated, restrictive or mixed
    • Arrhythmias – atrial tachycardias most common
  • Endocrine disease
  • 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
  • Chronic liver disease 
  • 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
Test Name and Number Recommended Use Limitations Follow Up
Iron and Iron Binding Capacity 0020420
Method: Quantitative Spectrophotometry

Aids in the diagnosis of iron deficiency, anemia, and iron overload

Quantitates serum or plasma iron; calculates values for transferrin saturation and TIBC (STS [%] = [100 x serum iron]/TIBC)

Should be fasting sample

   
Ferritin 0070065
Method: Quantitative Chemiluminescent Immunoassay

Aids in the diagnosis of iron deficiency, anemia, and iron overload

Monitor treatment for hemochromatosis

Elevated concentration alone not specific for iron overload

 
Hemochromatosis (HFE) 3 Mutations 0055656
Method: Polymerase Chain Reaction/Fluorescence Monitoring

Determine presence of HFE gene mutations (C282Y, H63D, S65C) in patients with iron overload; do not order HFE genetic testing for a patient without iron overload or a family history of HFE-associated hereditary hemochromatosis

Screening for adult family members of individuals with C282Y/C282Y or C282Y/H63D genotype

Carrier testing for reproductive partners of an individual with HH

Clinical sensitivity –

  • Up to 90% for Caucasian populations
  • Lower in other ethnicities

 Analytical sensitivity/specificity – 99%

Test should not be used for testing at-risk asymptomatic minors, population carrier screening, prenatal diagnosis

Genotyping does not substitute for serum iron studies, which identify iron overload

Only the 3 targeted HFE gene mutations will be detected

Rare diagnostic errors may occur due to primer-site mutations

Not recommended for asymptomatic patients <18 or prenatal diagnosis

If mutations are present, repeat STS and SF testing

Iron, Liver 0028250
Method: Quantitative Inductively Coupled Plasma-Mass Spectrometry

Useful in confirming hepatic iron overload, particularly in individuals with hemochromatosis and no common HFE mutations

Initial approach to diagnosis for hemochromatosis should include iron and iron binding capacity (NOTE: test includes serum transferrin saturation) and serum ferritin

Hepatic iron distribution may be heterogenous; verification of biopsy quality or testing multiple biopsy cores is preferred

 
Hepatitis B Surface Antigen by Immunohistochemistry 2003917
Method: Immunohistochemistry

Determine presence or absence of hepatitis

Stained and returned to client pathologist; consultation available if needed

   
Alpha-1-Antitrypsin (AAT) by Immunohistochemistry 2003424
Method: Immunohistochemistry

Identify fibrotic liver disease

Stained and returned to client pathologist; consultation available if needed

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
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