Hereditary hemochromatosis is a disorder in which iron is significantly absorbed by the digestive tract and accumulates in body tissues, which progressively causes diabetes, joint disorders, cardiac arrhythmia then heart failure, hepatic cirrhosis, skin color change, and increased risk of cancer. Organs commonly affected by hemochromatosis are the liver, heart, and endocrine glands.
Adult Hemochromatosis; Hereditary Hemochromatosis; Idiopathic Hemochromatosis.
Genetic disorder of iron metabolism described in 1865 by Trousseau and named from the Greek words heme (“of the blood”) and chroma (“color”).
Fewer than 1:250,000 per year in the general population, but approximately 1:200 people in the United States is believed to have a mutation necessary for iron overload. It is most common in certain European populations such as the Irish and Norwegians. It occurs in 0.6% of the population. Men with the disease are 24 times more likely to experience symptoms than affected women.
Autosomal recessive. Males are affected more severely with an earlier onset. Two mutations in the HFE gene can cause hereditary hemochromatosis: H63D (less severe and later onset form) and C282Y. HLA-A3 is found in 78.4% of cases (27% of controls) and HLA-B14 in 25.5% of cases (3.4% of controls). Gene located on 6p21.3, close to HLA-A locus. (See Table H-1.)
The HFE protein is normally expressed in crypt enterocytes of the duodenum (and the placenta) where it has a predominantly intracellular localization and forms a stable association with the transferrin receptor. The HFE protein is believed to modulate the uptake of transferrin-bound iron from plasma by crypt enterocytes. Impairment of this function could result in a paradoxical signal in crypt enterocytes, which causes them to absorb more dietary iron when they mature into villus enterocytes.
TABLE H-1Hemochromatosis: Genetic Mutations ||Download (.pdf) TABLE H-1 Hemochromatosis: Genetic Mutations
|Combination Mutations ||Patients with Hemochromatosis ||Patients without Symptoms ||Clinical Features |
|C282Y/C282Y ||60-90% ||7-50% ||Severe form |
|C282Y/H63D ||3% ||98-99.5% ||Moderate form |
|H63D/H63D ||1% ||>99% ||Mild form |
|C282Y/Normal ||Should not have symptoms and should be healthy carriers ||>99% ||Some patients may have mildly increased iron levels and a 1.5-2-fold increased risk for cardiac disorders |
Usually delayed until adulthood after onset of clinical symptoms, although screening of family members may lead to early, asymptomatic diagnosis. Orientation tests include serum ferritin, sideremia, and liver biopsy for iron staining, which are all consistent with iron accumulation. Diagnosis established by molecular biology on blood samples (presence of HFE mutation).
Symptomatology usually begins at middle age but may be detected earlier. Early symptoms are nonspecific: weakness, joint and ...