Haemochromatosis is a hereditary disease characterized by improper processing of iron in the body.
It is one the commonest inheritable genetic defects especially in people of northern European extraction, with about 1 in 10 people carrying the defective gene. There are two main genotypes: C282Y and H63D. C282Y is more serious and the greatest risk of haemochromatosis is for people with two copies of the abnormal gene. People with single copies are essentially normal. People with a copy of the C282Y gene and the H63D gene have a slight risk of haemochromatosis but are usually clinically normal.
Even if you have both copies of the abnormal gene the risk of actual clinical haemochromatosis is still quite low (? about 20%). This is called incomplete penetrance.
These figures are not exact because there is not a strict definition of heamochromatosis. The severity of the disease can vary greatly from person to person and also during a person's lifetime.
People with the abnormal genes do not reduce their absorption of iron in response to increased iron levels in the body. Thus the iron stores of the body increase. As they increase the iron which is initially stored as ferritin starts to get stored as a breakdown product of ferritin called haemosiderin and this is toxic to tissue.
see also cirrhosis
