Variable expressivity of HJV related hemochromatosis: "Juvenile" hemochromatosis?

Juvenile hemochromatosis is a rare autosomal recessive disease due to variants in the Hemojuvelin (HJV) gene. Although biological features mimic HFE hemochromatosis, clinical presentation is worst with massive iron overload diagnosed during childhood. Our study describes clinical features and results of genetic testing for a group of patients initially referred for a hepcidino-deficiency syndrome and for whom HJV hemochromatosis was finally diagnosed. 662 patients with iron overload and high serum transferrin saturation were tested, and five genes (HFE, HJV, HAMP, TFR2, SLC40A1) were sequenced. Among our cohort, ten unrelated patients were diagnosed with HJV hemochromatosis. Genetic testing revealed five previously published and five undescribed variants: p.Arg41Pro, p.His180Arg, p.Lys299Glu, p.Cys361Arg and p.Ala384Val. Surprisingly, this study revealed a late age of onset in some patients, contrasting with the commonly accepted definition of "juvenile" hemochromatosis. Five of our patients were 30 years old or older, including two very late discoveries. Biological features and severity of iron overload were similar in younger and older patients. Our study brings new insight on HJV hemochromatosis showing that mild phenotype and late onset are possible. Genetic testing for HJV variants should thus be performed for all patients displaying a non-p.Cys282Tyr homozygous HFE hemochromatosis with hepcidin deficiency phenotype.