How do you test for the C282Y (HFE gene) mutation in individuals suspected of having hereditary hemochromatosis, particularly those with a family history, Northern European descent, or symptoms suggestive of iron overload?

Testing for C282Y Mutation in Suspected Hereditary Hemochromatosis

Begin with serum iron studies (transferrin saturation and ferritin), then proceed to HFE genetic testing for C282Y and H63D mutations if iron parameters are elevated. 1

Initial Biochemical Screening

The first step is always biochemical assessment, not genetic testing 1:

• Measure transferrin saturation (TS) and serum ferritin simultaneously - never rely on a single test 1
• Diagnostic thresholds for proceeding to genetic testing:
  • Males: TS >50% and/or ferritin >300 μg/L 1
  • Females: TS >45% and/or ferritin >200 μg/L 1
  • Alternatively, any persistently elevated TS warrants genetic testing 1

When to Order HFE Genetic Testing

Order C282Y (and H63D) mutation analysis in these specific scenarios 1:

• Individuals of European descent with elevated iron parameters meeting the thresholds above 1
• Any patient with unexplained persistently elevated transferrin saturation, regardless of ferritin 1
• All adult first-degree relatives (>18 years) of patients with confirmed C282Y homozygous hemochromatosis - this is mandatory regardless of symptoms 1
• Patients with increased liver iron on MRI or biopsy 1
• Symptomatic patients with clinical signs suggestive of hemochromatosis (arthralgia, hepatomegaly, diabetes, cardiomyopathy, hypogonadism) even with borderline iron studies 1

The Genetic Test Itself

The test is HFE gene mutation analysis, which specifically looks for 1:

• C282Y mutation (the primary pathogenic variant - found in 85-90% of clinically affected patients) 2, 3
• H63D mutation (tested simultaneously, as compound heterozygotes C282Y/H63D can develop iron overload in ~20% of cases) 3, 4

This is typically performed via PCR-based methods with restriction enzyme digestion or direct DNA sequencing 5.

Critical Pre-Test Counseling Requirements

Before ordering genetic testing, you must discuss 1:

• Available treatment (phlebotomy) and its efficacy 1
• Costs of testing and ongoing monitoring 1
• Implications for insurability and employment 1
• Psychological impact of disease labeling 1
• Family screening implications (relatives will need testing) 1
• Possibility of uncertain or variant genotypes 1

Important Pitfalls to Avoid

Exclude secondary causes of elevated ferritin first 6:

• Chronic alcohol consumption 6
• Inflammatory conditions (ferritin is an acute phase reactant) 6
• Malignancy 6
• Non-alcoholic fatty liver disease/metabolic syndrome 6
• Active liver disease from any cause 6

Do not screen the general population - the USPSTF recommends against routine population screening due to low penetrance and potential harms of labeling 1, 7. Only perform targeted case-finding in high-risk individuals 7.

Recognize that genotype does not equal phenotype - approximately 10% of C282Y homozygotes develop clinically significant disease, and some homozygotes have no iron overload 2, 8. Conversely, some iron-loaded patients lack the C282Y mutation 8.

Family Screening Protocol

For first-degree relatives of confirmed cases 1, 7:

• Perform both HFE genetic testing AND phenotypic screening (TS and ferritin) simultaneously 7
• Siblings have the highest yield (33% homozygosity rate) 7
• This dual approach is essential because homozygosity alone is neither necessary nor sufficient for diagnosis 7

Assessment After Positive Genetic Testing

If C282Y homozygosity is confirmed, assess for advanced disease 1, 6:

• Liver biopsy is indicated if: 1, 6

  • Ferritin >1,000 μg/L 1
  • Elevated liver enzymes (ALT/AST) 1
  • Hepatomegaly on examination 1
  • Age >40 years 1
  • Platelet count <200 (predicts cirrhosis in 80% when combined with ferritin >1,000 μg/L and elevated transaminases) 6

• MRI can quantify hepatic iron non-invasively if the diagnosis is unclear or to assess extrahepatic organ involvement 1