Recently, two new types of hemochromatosis have been identified: Juvenile hemochromatosis (JH or HFE2), which maps to chromosome 1q21, and an adult form defined as HFE 3, which results from mutations of the TFR 2 gene, located at 7q22.
Human mutations in the glycosylphosphatidylinositol-anchored protein hemojuvelin (HJV; also known as RGMc and HFE2) cause juvenile hemochromatosis, a severe iron overload disease, but the way in which HJV intersects with the iron regulatory network has been unclear.
We report the occurrence of compound heterozygous mutations in hemojuvelin (HJV), including a termination codon, in a patient with juvenile hemochromatosis but no family history of iron disorders.
Altogether, the data demonstrate that the loss of HJV membrane export is central to the pathogenesis of JH, and that HJV cleavage is essential for the export.
One patient with severe iron overload was found to be a compound heterozygote for HJV mutations, one of which had previously been identified in patients with juvenile haemochromatosis (G320V) and the other was novel (C321W).
Four types of inherited iron overload have been recognized: type 1, the most common form with an autosomal recessive inheritance, is associated with mutations in the HFE gene on chromosome 6; type 2 (juvenile hemochromatosis) is an autosomal recessive disorder with causative mutations identified in the HJV gene (subtype A) on chromosome 1 and the HAMP gene (subtype B) on chromosome 19; type 3 has also an autosomal recessive inheritance with mutations in the TfR2 gene on chromosome 3; type 4 is an autosomal dominant condition with heterozygous mutations in the ferroportin 1 gene on chromosome 2.
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).
Human mutations in the glycosylphosphatidylinositol-anchored protein hemojuvelin (HJV; also known as RGMc and HFE2) cause juvenile hemochromatosis, a severe iron overload disease, but the way in which HJV intersects with the iron regulatory network has been unclear.