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Hemochromatosis type 2
Hemochromatosis type 2 (juvenile) is the early-onset and most severe form of rare hereditary hemochromatosis (HH; see this term), a group of diseases characterized by excessive tissue iron deposition of genetic origin.
ORPHA:79230Classification level: Disorder
HH type 2 is a rare disease (less than 100 reported cases) with a broad geographical distribution. Both sexes are equally affected.
Age of onset is usually less than 30 years. This juvenile form of hemochromatosis has the classical features of HH but is also characterized by severe cardiomyopathy and hypogonadism. Arthropathy, hepatic fibrosis, glucose intolerance, and increased skin pigmentation are frequent. Biochemical abnormalities include elevated serum iron, transferrin saturation and ferritin.
Two types of the disease have been described, both being transmitted in an autosomal recessive way. Type 2A, the most frequent form, is caused by mutations in the hemojuvelin (HFE2) gene on chromosome 1 and type 2B is caused by mutations in the hepcidin (HAMP) gene on chromosome 19. These mutations result in complete or major hepcidin deficiency, thus increasing drastically duodenal iron absorption and iron release from the spleen.
Diagnosis is based on biochemical testing for serum transferrin saturation (>90%), serum ferritin concentration (often >2000 microg/L), and on magnetic resonance imaging (MRI) for diagnosing visceral (especially hepatic and cardiac) iron overload. Molecular genetic blood testing allows, in most cases, the diagnosis to be established in a non invasive way (i.e. without a liver biopsy).
Differential diagnosis includes hemochromatosis type 3 (see this term) and post-transfusional iron overload in the case of hematological diseases such as thalassemia major, sickle cell disease, and other rare anemias (see these terms).
Genetic counseling should be offered to affected families, informing them of the risk of inheriting the disease-causing mutation in an autosomal recessive manner.
Management and treatment
Intensive phlebotomies, sometimes combined with iron chelation therapy, form the basis of treatment.
Complications like heart failure are often fatal. Early and intensive iron depletive therapy can significantly improve an otherwise devastating prognosis.
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