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Copper Deficiency and Toxicity
Copper is a component of many body proteins; almost all of the body’s copper is bound to copper proteins. Unbound (free) copper ions are toxic. Genetic mechanisms control the incorporation of copper into apoproteins and the processes that prevent toxic accumulation of copper in the body. Copper absorbed in excess of metabolic requirements is excreted through bile.
If the genetic mechanisms controlling copper metabolism are normal, dietary deficiency rarely causes clinically significant copper deficiency. Causes include
Deficiency may cause neutropenia, impaired bone calcification, myelopathy, neuropathy, and hypochromic anemia not responsive to iron supplements.
Diagnosis is based on low serum levels of copper and ceruloplasmin, although these tests are not always reliable.
Treatment is directed at the cause, and copper 1.5 to 3 mg/day po (usually as copper sulfate) is given.
Inherited copper deficiency occurs in male infants who inherit a mutant X-linked gene. Incidence is about 1 in 100,000 to 250,000 live births. Copper is deficient in the liver, serum, and essential copper proteins, including cytochrome-c oxidase, ceruloplasmin, and lysyl oxidase.
Diagnosis of inherited copper deficiency is based on low copper and ceruloplasmin levels in serum. Because early diagnosis and treatment seem to result in a better prognosis, the disorder is ideally detected before age 2 wk. However, diagnostic accuracy of these tests is limited. Thus, other tests are being developed.
Acquired copper toxicity can result from ingesting or absorbing excess copper (eg, from ingesting an acidic food or beverage that has had prolonged contact with a copper container). Self-limited gastroenteritis with nausea, vomiting, and diarrhea may occur.
More severe toxicity results from ingestion (usually with suicidal intent) of gram quantities of a copper salt (eg, copper sulfate) or from absorption of large amounts through the skin (eg, if compresses saturated with a solution of a copper salt are applied to large areas of burned skin). Hemolytic anemia and anuria can result and may be fatal.
Indian childhood cirrhosis, non-Indian childhood cirrhosis, and idiopathic copper toxicity are probably identical disorders in which excess copper causes cirrhosis. All appear to be caused by ingesting milk that has been boiled or stored in corroded copper or brass vessels. Studies suggest that idiopathic copper toxicity may develop only in infants with an unknown genetic defect.
Diagnosis usually requires liver biopsy, which may show Mallory hyalin bodies.
For copper toxicity due to ingesting grams of copper, prompt gastric lavage is done. Copper toxicity that causes complications such as hemolytic anemia, anuria, or hepatotoxicity is also treated with either oral penicillamine 250 mg q 6 h to 750 mg q 12 h (1000 to 1500 mg/day in 2 to 4 doses) or dimercaprol 3 to 5 mg/kg IM q 4 h for 2 days, then q 4 to 6 h ( chelation therapy).
If used early, hemodialysis may be effective.
Occasionally, copper toxicity is fatal despite treatment.
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