The clinical significance of C282Y homozygosity is well established, with emerging evidence demonstrating that compound heterozygosity (C282Y/H63D) can also result in clinically relevant iron overload, and impaired quality of life in a subset of patients. Our Summer Research Intern, Leah has worked over the Summer to investigate the impact of different genotypes on people’s Quality of Life. The finalised paper can be read below.

Recent publications have argued that the H63D variant lacks diagnostic or clinical utility and should no longer be included in standard genetic testing panels. However, this interpretation risks overlooking patients with compound genotypes who may develop symptomatic disease and could benefit from appropriate monitoring and intervention.

Multiple independent studies have now provided robust evidence that challenges the dismissal of C282Y/H63D compound heterozygosity as clinically irrelevant:

• Therkildsen et al. (2022, Scandinavian Journal of Gastroenterology) analysed 203 patients in a single-centre Copenhagen cohort.
• Nearly one-third were compound heterozygotes.
• Although C282Y homozygotes had higher mean ferritin and transferrin saturation, the prevalence of symptoms and organ complications did not differ significantly between the two genotypes.
• The authors concluded that compound heterozygotes should be assessed and managed similarly to classical homozygotes when clinical or biochemical evidence of iron overload is present.
• The HFE Genotype Quality-of-Life Study (2025) compared WHOQOL-100 outcomes across HFE genotypes.
• Participants with C282Y/H63D compound heterozygosity reported marked reductions in quality of life, fatigue, arthropathy, and psychological distress comparable to those with C282Y homozygosity.
• The study found no significant difference in symptom burden between genotypes, emphasising that genotype alone does not predict clinical impact.

Quality of Life in People Diagnosed with Genetic Haemochromatosis Paper

Collectively, these studies underscore that compound heterozygosity is not a benign state and can result in meaningful iron-related pathology, especially when compounded by age, comorbidities, or environmental cofactors such as alcohol intake or metabolic syndrome.

In light of the growing clinical and empirical evidence, we do not support the recommendation to remove the H63D variant from diagnostic reporting or surveillance criteria. Instead, we advocate for a comprehensive and phenotype-driven approach that ensures equitable assessment of all patients with demonstrable iron overload.

We therefore recommend that:

1. Genetic testing for HFE mutations continues to include both C282Y and H63D to enable accurate identification of compound heterozygotes.
2. Compound heterozygotes (C282Y/H63D) with elevated serum ferritin and transferrin saturation should be monitored regularly, and treatment (e.g., venesection) should be initiated when clinically indicated.
3. Clinical management should be guided by biochemical findings, symptoms, and organ involvement, rather than genotype alone.
4. Healthcare professionals should receive updated education and guidance to recognise the potential clinical expression of compound heterozygosity.
5. Patient communication should be accurate, avoiding misleading reassurance that C282Y/H63D is harmless, while also preventing unnecessary anxiety in asymptomatic individuals.

The current evidence base does not support excluding the C282Y/H63D genotype from diagnostic relevance in genetic haemochromatosis. While not all compound heterozygotes develop significant iron overload, a proportion clearly do, and benefit from timely detection and management as a preventive health intervention.

A phenotype-informed, inclusive, and evidence-based approach is essential to avoid underdiagnosis, reduce delayed treatment, and improve patient outcomes. The H63D variant, particularly in compound heterozygous form, remains clinically meaningful and should continue to inform diagnostic and therapeutic decisions in genetic haemochromatosis.

Quality of Life in People Diagnosed with Genetic Haemochromatosis - Summary: https://www.haemochromatosis.org.uk/News/quality-of-life-in-people-diagnosed-with-genetic-haemochromatosis Full Paper download

Palmer, W. C., & Stancampiano, F. F. (2025). Hemochromatosis. Annals of Internal Medicine, 178(2), ITC17–ITC32. https://doi.org/10.7326/annals-24-03710

Therkildsen, R., Dahl, E. E., & Schiødt, F. V. (2022). Hereditary hemochromatosis: data from a single center Copenhagen cohort. Scandinavian Journal of Gastroenterology, 57(8), 972–977. https://doi.org/10.1080/00365521.2022.2042591