Abstract
Copper is an essential trace element required by all living organisms. Excess amounts of copper, however, results in cellular damage. Disruptions to normal copper homeostasis are hallmarks of three genetic disorders: Menkes disease, occipital horn syndrome, and Wilson’s disease. Menkes disease and occipital horn syndrome are characterized by copper deficiency. Typical features of Menkes disease result from low copper-dependent enzyme activity. Standard treatment involves parenteral administration of copper-histidine. If treatment is initiated before 2 months of age, neurodegeneration can be prevented, while delayed treatment is utterly ineffective. Thus, neonatal mass screening should be implemented. Meanwhile, connective tissue disorders cannot be improved by copper-histidine treatment. Combination therapy with copper-histidine injections and oral administration of disulfiram is being investigated. Occipital horn syndrome characterized by connective tissue abnormalities is the mildest form of Menkes disease. Treatment has not been conducted for this syndrome.Wilson’s disease is characterized by copper toxicity that typically affects the hepatic and nervous systems severely. Various other symptoms are observed as well, yet its early diagnosis is sometimes difficult. Chelating agents and zinc are effective treatments, but are inefficient in most patients with fulminant hepatic failure. In addition, some patients with neurological Wilson’s disease worsen or show poor response to chelating agents. Since early treatment is critical, a screening system for Wilson’s disease should be implemented in infants. Patients with Wilson’s disease may be at risk of developing hepatocellular carcinoma. Understanding the link between Wilson’s disease and hepatocellular carcinoma will be beneficial for disease treatment and prevention.
Highlights
Copper is an essential element required by cuproenzymes, including cytochrome C oxidase, lysyl oxidase, dopamine ßhydroxylase, superoxide dismutase, tyrosinase, ascorbic acid oxidase, and ceruloplasmin
Each disease is caused by the absence of or defect in two copper-transporting ATPases encoded by the ATP7A gene [7,8,9,10,11] and ATP7B gene [12,13,14,15]
If the delivery of copper into the trans-Golgi apparatus of affected cells could be achieved, copper treatment would probably normalize the activity of lysyl oxidase and improve connective tissue disorders associated with Menkes (kinky hair) disease (MD) and occipital horn syndrome (OHS)
Summary
Copper is an essential element required by cuproenzymes, including cytochrome C oxidase, lysyl oxidase, dopamine ßhydroxylase, superoxide dismutase, tyrosinase, ascorbic acid oxidase, and ceruloplasmin. Each disease is caused by the absence of or defect in two copper-transporting ATPases encoded by the ATP7A gene (responsible for MD and OHS) [7,8,9,10,11] and ATP7B gene (responsible for WD) [12,13,14,15]. MD and OHS, for example, are characterized by copper deficiency, and WD by toxicity due to excess copper. This difference relates to the particular cell type expressing ATP7A and ATP7B. We review genetic disorders of copper transport, and highlight clinical problems relating to their diagnosis and treatment
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