Disorders of trace element metabolism represent an important class of human diseases.The best known of these reflect abnormalities in iron, copper or zinc metabolism.These diseases can lead to a deficiency of the metal in the tissues (e.g.matriptase 2 deficiency for iron, Menkes disease for copper, acrodermatitis enteropathica for zinc) or an excess (e.g.haemochromatosis for iron, Wilson disease for copper).Some disorders may also affect the homeostasis of multiple metals.