Volume 128, Issue 2, Pages 470-479 (February 2005) Juvenile hemochromatosis associated with pathogenic mutations of adult hemochromatosis genes  Antonello Pietrangelo, Angela Caleffi, Jean Henrion, Francesca Ferrara, Elena Corradini, Hasan Kulaksiz, Wolfgang Stremmel, Pietro Andreone, Cinzia Garuti  Gastroenterology  Volume 128, Issue 2, Pages 470-479 (February 2005) DOI: 10.1053/j.gastro.2004.11.057 Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 1 Pedigree of the family. Male and female family members are represented by squares and circles, respectively; solid symbols indicate individuals with phenotypically expressed hemochromatosis. Below the symbol for each family member are the age at diagnosis and the ferritin level (nanograms per milliliter). The pedigree shows consanguinity in subjects III-1 and III-2 and biochemical iron overload in 3 of their 5 children. Gastroenterology 2005 128, 470-479DOI: (10.1053/j.gastro.2004.11.057) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 2 Liver biopsy specimens from the 3 siblings with iron overload at the time of diagnosis. Perls’ Prussian blue stain was used to detect the presence of iron (A, C, and E), and Sirius red was used to detect the presence of collagen (B, D, and F). (A) and (B) (original magnification 533×) show the specimen from the proband, subject IV-4, whose hepatic iron concentration was 411 μmol/g of liver (dry weight). (C) and (D) (original magnification 533×) show the specimen from his affected sister (subject IV-5; hepatic iron concentration, 429 μmol/g). In both cases, massive iron overload is evident throughout the hepatic lobules, and deposits are found predominantly in parenchymal cells. An iron-free focus (arrowheads) can also be seen in the specimen from subject IV-5 (C). Both specimens show cirrhotic nodularity (B and D). (E) and (F) (original magnification 133×) show the specimen from subject IV-2, who, at the time of diagnosis, was asymptomatic, with a hepatic iron concentration of 62 μmol/g of liver (dry weight). Although the iron overload is milder than that of subjects IV-4 and IV-5, its distribution pattern is characteristic of hereditary hemochromatosis: iron deposits are found almost exclusively within the parenchymal cells in periportal areas, with a granular pattern and a pericanalicular distribution (inset). Only minimal periportal fibrosis and some sinusoidal fibrosis (square) are appreciable (F). Gastroenterology 2005 128, 470-479DOI: (10.1053/j.gastro.2004.11.057) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 3 Chromosome 1 haplotype analysis of family members. Circles represent female family members, squares male family members, and solid symbols members with hemochromatosis. Haplotypes were constructed on the basis of analysis of 4 microsatellite markers (D1S2344, D1S2442, D1S2347, and D1S2343) spanning the 1q region of chromosome 1, where the HJV gene lies. The allelic forms of each of the 4 markers (ie, the forms found on the 2 chromosomes 1) are indicated by numbers (eg, 237 and 253 are variants found at locus D1S2344). The 4-locus haplotypes found in the father (haplotypes A1 and A2) and mother (haplotypes B1 and B2) are randomly transmitted to the 5 children. The presence (+) or absence (−) of the TfR2 Q317X mutation and the HFE C282Y and H63D mutations is indicated beneath each chromosome 1q haplotype. Hemochromatosis in this family displayed no linkage to chromosome 1q. In fact, haplotype A2B2 was found in the proband and in an unaffected brother. The second unaffected sibling was A1B2, the same haplotype found in siblings IV-2 and IV-5, who had phenotypically different forms of the disease. All 3 affected siblings were homozygous for TfR2 Q317X, but the 2 with juvenile hemochromatosis were also compound HFE C282Y/H63D heterozygotes. Gastroenterology 2005 128, 470-479DOI: (10.1053/j.gastro.2004.11.057) Copyright © 2005 American Gastroenterological Association Terms and Conditions

Figure 4 A unifying pathogenic model for hereditary hemochromatosis (HH): hepcidin as a common denominator. In this model, HFE, TfR2, and HJV are considered independent but complementary modulators of hepcidin synthesis/activity, which down-regulates the rate at which intestinal cells and macrophages release iron into the bloodstream. When all 3 proteins function correctly (and the HAMP gene that encodes hepcidin is normal), the amount of iron transferred into the blood will be appropriate to body needs, and excessive iron deposition in tissues will be avoided. The relative contributions of the 3 genes to this modulatory process have been arbitrarily represented in the figure: the more substantial role assigned to HJV (50% vs. 25% each for the “minor” regulators, HFE and TfR2) reflects the more severe iron overload phenotype associated with HJV mutations. Loss of one of the minor regulatory proteins (HFE- or TfR2-related HH) will result in an appreciable increase in iron influx into the bloodstream, but residual hepcidin activity will be sustained by the second minor regulator and the major regulator, the HJV gene. The result is a mild “adult” hemochromatosis phenotype, with gradual plasma iron loading and gradual accumulation of iron in tissues. Combined loss of HFE and TfR2 (HFE+TfR2-related HH) will result in much more rapid and substantial increases in plasma iron, and, consequently, greater iron overload in tissues: in short, a more severe juvenile phenotype, not unlike the one produced by loss of the major hepcidin regulator, HJV. Finally, the complete loss of hepcidin (HAMP-related HH), despite normal HFE, TfR2, and HJV, will inevitably lead to massive uncontrolled release of iron into the circulation. Gastroenterology 2005 128, 470-479DOI: (10.1053/j.gastro.2004.11.057) Copyright © 2005 American Gastroenterological Association Terms and Conditions