Relationship between Serum Copper, Ceruloplasmin, and Non–Ceruloplasmin-Bound Copper in Routine Clinical Practice

Copper is an essential cofactor for many enzymes, including cytochromes, but it is toxic in its unbound form. The vast majority of serum copper is transported bound to ceruloplasmin; the rest is bound to albumin, transcuprein, and copper–amino acid complexes. Wilson disease, an autosomal recessive disorder with a frequency of 1 in 30 000 to 1 in 100 000 live births, is caused by mutations in a P-type ATPase that prevent the incorporation of copper into ceruloplasmin (1)(2). Copper deposition occurs in hepatic parenchymal cells, the brain, the periphery of the iris, and the kidney. The age of onset and form of presentation of Wilson disease are very variable. Initially, copper accumulates in the liver, and accordingly, hepatic presentations are common (1)(2). Diagnosis of Wilson disease is a challenge (3), particularly in the absence of obvious neurologic changes, Kayser–Fleisher rings, and ophthalmic slit lamp eye examination. Low serum copper and low serum ceruloplasmin concentrations are usually seen, but some patients have concentrations within the reference intervals (2)(3)(4). Serum copper is influenced by age, acute-phase reactions, pregnancy, many anemias, and medication (oral contraceptives and antiepileptics) (5). Furthermore, ∼2% of the population who are heterozygous for P-type ATPase …