The iron reabsorption index: a new phenotypic and pathophysiological descriptor in HFE hemochromatosis.

Background: The current phenotypic descriptors of high Fe gene hemochromatosis are hardly specific and time dependent in a context of highly variable expressivity. We hypothesized that the rate of iron removed during maintenance therapy and corresponding to the iron reabsorption index (IRI) could be patient specific and may then represent a new useful phenotypic marker.

Aim: The present study aimed to describe IRI with respect to its phenotypic specificity and to its potential usefulness.

Methods: We studied a cohort of 316 p.Cys282Tyr homozygous patients with stable low serum ferritin levels on maintenance therapy for at least 12 months. Characteristics at diagnosis, date and volume of phlebotomies, and parameters of iron metabolism throughout maintenance therapy were determined.

Results: IRI ranged from 1.3 to 6.1 mg/day (median: 2.44). It was lower in women (difference: 1.26 mg/day), mainly explained by physiological blood loss, weight, and alcohol consumption. IRI was correlated to iron burden and fibrosis stage at diagnosis, was stable over time (variation: 11.5%), and depended on serum ferritin level during therapy.

Conclusion: Its independence from disease duration, its stability, its wide distribution, and its significant correlation with iron burden markers make IRI a valuable potential phenotypic indicator of the daily iron overabsorption in hemochromatosis. Moreover, IRI provides a conceptual frame for empiric adaptation of maintenance therapy.