What is hemochromatosis?
Hemochromatosis is an iron metabolism disorder that may be inherited or acquired. People with hemochromatosis accumulate more iron than their body needs. As the body does not have a way to excrete excess iron, there is a progressive buildup of iron in tissues and organs. Eventually, the iron overload can lead to dysfunction and failure of several organs, notably the heart, liver, and endocrine portion of the pancreas. Complications include arthritis, diabetes, liver cirrhosis, heart arrhythmias and failure, and an increase in skin pigmentation termed "bronzing."
There are two types of hemochromatosis: primary hemochromatosis, an inherited form that is passed from one generation to the next, and secondary hemochromatosis, which is caused by some other disease or underlying condition.
Primary or Hereditary Hemochromatosis
Hereditary hemochromatosis (HH), also called primary hemochromatosis, is one of the most common genetic disorders in the U.S., affecting about one million people, most of them Caucasians. HH is an autosomal recessive disorder, which means that it is associated with two abnormal gene copies. Approximately 1 in 10 Caucasians have one abnormal (or mutated) copy of the gene associated with hereditary hemochromatosis, the HFE gene, and are called carriers. Carriers are not at risk for developing iron overload. About 1 in every 300 Caucasians has two mutated copies of the HFE gene and is at risk for developing iron overload and clinical symptoms. However, most people who carry two mutated genes never develop signs and symptoms of the disease. The reason for this is unknown, and research is ongoing to determine the percentage of individuals who eventually become sick with the disease.
HH affects more men than women, and symptoms of the disorder emerge at an earlier age for men, typically at about 30 to 50 years old. Two other rare forms of inherited hemochromatosis, neonatal and juvenile hemochromatosis, can cause severe iron overload in children and young adults. These disorders are caused by mutations in a different gene, one called hemojuvelin. In fact, a small percentage of cases of HH are due to mutations in genes coding for other proteins, including hemojuvelin as well as transferrin-receptor 2 and ferroportin. Tests for these mutations are not widely available, however.
Secondary or Acquired Hemochromatosis
Secondary hemochromatosis is an acquired iron overload that can be due to a variety of other diseases and conditions. Examples include chronic liver disease, some forms of anemia, recurrent blood transfusions, and rarely, oral iron supplementation.