Ironing out disease: inherited disorders of iron homeostasis

Iron presents us with a paradox. Without it, cells simply cannot survive because iron is an essential cofactor for many enzymes in critical biochemical pathways. However, when iron is present in excess, it can be highly cytotoxic due to its propensity to catalyze the formation of reactive oxygen radicals. To cater for this dual nature, cells and organisms have developed elaborate mechanisms for regulating iron intake and efflux. When these mechanisms are disrupted, as is the case in a number of inherited disorders of iron metabolism, the pathological consequences can be severe. Many of these disorders are characterized by iron overload and include relatively common diseases such as hereditary hemochromatosis, rare abnormalities of plasma protein synthesis (atransferrinemia and aceruloplasminemia), and the neuromuscular disease Friedreich ataxia. The few described inherited anemias in humans have yet to yield to molecular dissection, but the investigation of several rodent anemias has proved highly rewarding. This review will provide a summary of some of these disorders and describe how their analysis has provided important new insights into iron trafficking pathways and their regulation.