The data show that heterozygous mutations of the hemojuvelin gene contribute like those of hepcidin to the phenotypic heterogeneity of hemochromatosis.
Mutations in HAMP and HJV genes and their impact on expression of clinical hemochromatosis in a cohort of 100 Spanish patients homozygous for the C282Y mutation of HFE gene.
Here, we report a heterozygous genotype at two mutation sites in hemojuvelin (HJV) present in two brothers with middle-age-onset hemochromatosis in a Chinese family.
We conclude that homozygosity for HJVR54X accounts for his severe, early age-of-onset hemochromatosis; his phenotype was probably modified by serial phlebotomy therapy.
We used a standard 96-well microplate with a single PCR condition in an adaptation of the SCAIP (single-condition amplification with internal primer) method to sequence the HFE (hemochromatosis), HAMP (hepcidin antimicrobial peptide), HFE2/HJV [hemochromatosis type 2 (juvenile)], SLC40A1 (ferroportin), and TFR2 (transferrin receptor 2) genes, and the 5' untranslated region of the FTL (ferritin, light polypeptide) gene.
The term hemochromatosis should refer to a unique clinicopathologic subset of iron-overload syndromes that currently includes the disorder related to the C282Y homozygote mutation of the hemochromatosis protein HFE (by far the most common form of hemochromatosis) and the rare disorders more recently attributed to the loss of transferrin receptor 2, HAMP (hepcidin antimicrobial peptide), or hemojuvelin or to certain ferroportin mutations.
We addressed the question of whether hemojuvelin mutations may influence the phenotype of patients with adult-onset haemochromatosis with or without mutations of the HFE gene.
Juvenile hereditary hemochromatosis is not a distinct monogenic disorder invariably due to hemojuvelin or hepcidin mutations: it may be genetically linked to the adult-onset form of hereditary hemochromatosis.
To date, four types of hemochromatosis have been identified: HFE-related or type1 hemochromatosis, the most frequent form in Caucasians, and four rare types, named type 2 (A and B) hemochromatosis (juvenile hemochromatosis due to hemojuvelin and hepcidin mutation), type 3 hemochromatosis (related to transferrin receptor 2 mutation), and type 4 (A and B) hemochromatosis (ferroportin disease).
The identification of HFE, the principal determinant of adult haemochromatosis (HFE1; OMIM 235200) and TfR2, recently implicated in a rarer form of the inherited disorder (HFE3; OMIM 604250), and the promise of candidate genes for juvenile haemochromatosis (HFE2; OMIM 602390) and neonatal haemochromatosis (OMIM 231100) provide the foundation for important studies into the control mechanism of iron balance in humans.
Our results clarify the natural history of the disease and are compatible with the hypothesis that the HFE2 gene has greater influence on iron absorption than other haemochromatosis-associated genes.