Reduced oxidase activity in the caeruloplasmin of two families with Wilson's disease.

Caeruloplasmin has been determined immunologically and by coper oxidase activity in 25 normal subjects, 20 patients with Wilson's disease, and 80 patients with chronic liver disease. Repeated estimation in four patients with Wilson's disease and two heterozygous mothers from two families revealed a consistent reduction in the copper oxidase activity of caeruloplasmin (12-32 units copper oxidase activity/mg caeruloplasmin) relative to the values obtained in normal subjects, patients with chronic liver disease, and other Wilson's disease patients (mean 65-79 units/mg). It is suggested that the functional abnormality in caeruloplasmin observed in these two families is an inherited variant, which does not appear to be due to the presence of a serum inhibitor of copper oxidase.