What genes should be included in a hemochromatosis (iron overload disorder) gene panel?

Hemochromatosis Gene Panel Composition

A comprehensive hemochromatosis gene panel should include five core genes: HFE, HJV (hemojuvelin), HAMP (hepcidin), TFR2 (transferrin receptor-2), and SLC40A1 (ferroportin), as these account for all recognized forms of hereditary hemochromatosis. 1

Primary Gene: HFE

HFE is the essential starting point, as it accounts for 85-90% of all hereditary hemochromatosis cases. 1 The panel must specifically test for:

• C282Y mutation (most critical - found in >90% of hemochromatosis patients) 2
• H63D mutation (compound heterozygotes C282Y/H63D represent 3-5% of cases) 2
• S65C mutation (less common but clinically relevant) 1
• Other HFE mutations should be included via sequencing rather than just targeted mutation analysis 3

Non-HFE Genes (10-15% of Cases)

The remaining 10-15% of hereditary hemochromatosis patients have mutations in non-HFE genes, making their inclusion essential for comprehensive diagnosis. 1

HJV (Hemojuvelin Gene)

• Most common cause of juvenile hemochromatosis 1
• Located on chromosome 1q 1
• Characterized by rapid iron accumulation with cardiac and endocrine manifestations typically before age 30 4
• The G320V mutation is a key variant to identify 4

HAMP (Hepcidin Gene)

• Codes for hepcidin, the principal iron-regulatory hormone 1
• Causes juvenile hemochromatosis but is much less common than HJV mutations 1
• Novel mutations like R59X have been identified 3

TFR2 (Transferrin Receptor-2 Gene)

• Causes adult-onset hemochromatosis similar to HFE-related disease 1, 5
• Clinically relevant in certain populations (e.g., AVAQ 594-597 deletion found in Iranian patients) 6
• Novel mutations like D555N continue to be discovered 3

SLC40A1 (Ferroportin Gene)

• Causes ferroportin disease (hemochromatosis type 4) 1
• Unique autosomal dominant inheritance pattern (unlike other forms which are autosomal recessive) 5
• Distinct phenotype with reticuloendothelial iron loading rather than parenchymal 5

Clinical Testing Algorithm

When to order comprehensive gene panel testing:

• Elevated transferrin saturation (>45%) and/or elevated ferritin (>300 ng/mL men, >200 ng/mL women) with negative or non-diagnostic HFE testing 7
• Unexplained iron overload after excluding secondary causes 4, 3
• Young patients (<30 years) with iron overload and cardiac/endocrine manifestations (suspect HJV) 4
• Family history of hemochromatosis with atypical presentation 7

Geographic and Population Considerations

The utility of different genes varies by population:

• Northern European ancestry: HFE mutations predominate (C282Y allele frequency ~6.2%) 2
• Mediterranean populations: Up to 30% of iron overload cases are non-HFE related, making comprehensive panels more critical 3
• Non-European populations: Lower HFE mutation prevalence necessitates broader genetic testing 6

Testing Methodology

Next-generation sequencing (NGS) is superior to targeted mutation analysis because:

• Identifies novel and rare/private mutations not detected by traditional methods 3
• More cost-effective than sequential Sanger sequencing of multiple genes 3
• Particularly valuable in populations where common HFE mutations are less prevalent 6, 3

Common Pitfalls to Avoid

• Testing only for C282Y and H63D mutations: This misses 10-15% of hereditary hemochromatosis cases and virtually all non-HFE cases 1
• Assuming negative HFE testing excludes hereditary hemochromatosis: Always consider non-HFE genes in patients with unexplained iron overload 3
• Overlooking ferroportin disease: This has dominant inheritance and different clinical features requiring different management 5
• Not considering age of presentation: Juvenile onset (<30 years) strongly suggests HJV or HAMP mutations 4