A 38-year-old man is referred for persistently elevated serum ferritin of 2,400 ng/mL and transferrin saturation of 72% over 6 months. He has no alcohol history. HFE gene testing shows he is homozygous for C282Y mutation. Liver biopsy shows hepatic iron concentration (HIC) of 220 µmol/g dry weight (normal < 36). The hepatic iron index (HII = HIC/age in years) is calculated. What HII value confirms hereditary haemochromatosis (HH)?
- A HII > 1.9 ✓
- B HII > 1.0
- C HII > 0.5
- D HII > 2.5
Explanation
The Hepatic Iron Index (HII) = hepatic iron concentration (in µmol/g dry weight) divided by age in years. An HII > 1.9 is the established threshold that distinguishes hereditary haemochromatosis (type 1, HFE-related) from other causes of hepatic iron overload such as alcoholic liver disease, dysmetabolic iron overload syndrome, or heterozygous HFE carriers. In this patient: HII = 220/38 = 5.8, which far exceeds 1.9, consistent with HH. This calculation is now less often needed since HFE genotyping confirms C282Y homozygosity, but the HII remains the histological confirmatory criterion for clinical decisions including transplant evaluation and quantifying iron burden.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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