The role of the clinical biochemist in detection of zinc-induced copper deficiency.

A middle-aged woman with neutropenia and ataxia was found to have raised plasma zinc and profoundly low plasma copper concentrations. When found that she had been prescribed 135 mg zinc/day for seven years, a diagnosis of zinc-induced copper deficiency was made. After the zinc prescription was stopped, her copper and zinc concentrations and neutropenia normalized but she only had partial improvement in neurological status. The diagnosis of zinc-induced copper deficiency can be facilitated by the laboratory through measurement of plasma zinc concentration in patients with a low plasma copper concentration.