Copper is an essential metal that is an important cofactor for many proteins and enzymes. Two related genetic defects in copper transport have been described, each with distinct phenotypes. Wilson’s disease—an uncommon disorder (1 in 30 000) caused by autosomal recessive loss-of-function mutations in a metal-transporting P-type ATPase (ATP7B) that result in defective copper excretion into bile and hence copper toxicity. Typical presentation is in the second and third decade of life with liver disease (ranging from asymptomatic to acute fulminant hepatic failure or chronic end-stage liver disease) or neurological or psychiatric disorder (dystonia, dysarthria, parkinsonian tremor, movement disorder, a spectrum of psychiatric ailments). While no single biochemical test or clinical finding is sufficient for establishing the diagnosis, typical findings include low serum ceruloplasmin, high urinary copper excretion, and elevated liver copper content. Corneal Kayser–Fleischer rings may be seen. Treatment is with copper chelating agents and zinc. Liver transplantation is required for fulminant hepatic failure and decompensated liver disease unresponsive to medical therapy. Menkes’ disease—a rare disorder (1 in 300 000) caused by X-linked loss-of-function mutations in a P-type ATPase homologous to ATP7B (ATP7A) that result in defective copper transport across intestine, placenta, and brain and hence cellular copper deficiency. Clinical presentation is in infancy with facial dimorphism, connective tissue disorder, hypopigmentation, abnormal hair, seizures, and failure to thrive, usually followed by death by age 3 years (although some variants with a milder phenotype result from milder mutations, e.g. occipital horn syndrome). Treatment, which is only effective when presymptomatic diagnosis is made in a sibling after florid presentation in a previous affected sibling, is with intravenous copper histidine.
Direct sequencing of mutations in the copper-transporting P-type adenosine triphosphate (ATP7B) gene for diagnosis and pathogenesis of Wilson’s disease
