miércoles, 21 de diciembre de 2011

VACTERL association - Genetics Home Reference

VACTERL association - Genetics Home Reference

African iron overload

What is African iron overload?

African iron overload is a condition that involves absorption of too much iron from the diet. The excess iron is stored in the body's tissues and organs, particularly the liver, bone marrow, and spleen. Humans cannot increase the excretion of iron, although some iron is lost through bleeding or when cells of the intestine (enterocytes) are shed at the end of the cells' lifespan. Iron levels in the body are primarily regulated through control of how much iron is absorbed from the diet.

African iron overload results from a diet high in iron. It is particularly associated with consumption of a traditional African beer that contains dissolved iron from the metal drums in which it is brewed. Some evidence suggests that a genetic predisposition to absorbing too much iron may also be involved.

In African iron overload, excess iron typically accumulates in liver cells (hepatocytes) and certain immune cells called reticuloendothelial cells. Reticuloendothelial cells include macrophages in the bone marrow and spleen and Kuppfer cells, which are specialized macrophages found in the liver. Kuppfer cells and other macrophages help protect the body against foreign invaders such as viruses and bacteria.

When too much iron is absorbed, the resulting iron overload can eventually damage tissues and organs. Iron overload in the liver may lead to chronic liver disease (cirrhosis) in people with African iron overload. Cirrhosis increases the risk for developing a type of liver cancer called hepatocellular carcinoma. Iron overload in immune cells may affect their ability to fight infections. African iron overload is associated with an increased risk of developing infections such as tuberculosis.

People with African iron overload may have a slightly low number of red blood cells (mild anemia), possibly because the iron that accumulates in the liver, bone marrow, and spleen is less available for production of red blood cells. Affected individuals also have high levels of a protein called ferritin in their blood, which can be detected with a blood test. Ferritin stores and releases iron in cells, and cells produce more ferritin in response to excess amounts of iron.

How common is African iron overload?

African iron overload is common in rural areas of central and southern Africa; up to 10 percent of the population in these regions may be affected. Men seem to be affected more often than women, possibly due to some combination of differences in dietary iron consumption and gender differences in the processing of iron.

The prevalence of increased iron stores in people of African descent in other parts of the world is unknown; however, these individuals may be at higher risk of developing mildly increased iron stores than are people of European background.

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