Long-Term Urinary Copper Excretion and Exchangeable Copper in Children With Wilson Disease Under Chelation Therapy

Determining 24-hour urinary copper excretion (UCE) levels is useful for diagnosing Wilson's disease (WD) and for treatment monitoring. Exchangeable copper (ExC) is a novel potential marker, but its long-term changes have never been described in patients under chelation therapy. Our aim was to describe the long-term changes in ExC levels compared to UCE levels in symptomatic WD pediatric patients under chelation therapy.

A retrospective, descriptive, and analytical study including all patients under 18 years of age, diagnosed between 2006 and 2020, and treated with chelation therapy was conducted at the National Reference Center for WD in Lyon. Ceruloplasmin levels, serum copper, 24 h-UCE, ExC, and liver enzymes at diagnosis and during follow-up were analyzed.

Our study included 36 patients, predominantly with hepatic form of WD (n = 31). The median [interquartile range (IQR)] age at diagnosis was 10.5 (8.4-13.1) years, and the median (IQR) follow-up duration was 6.3 (3.3-8.8) years. At diagnosis, the median (IQR) ExC value was 1.01 (0.60-1.52) µmol/L. There was a significant decrease during the first year of chelation treatment ( P = 0.0008), then a stabilization. The median (IQR) ExC values was 0.38 (0.22-0.63) µmol/L at 12-18 months and 0.43 (0.31-0.54) µmol/L at 5 years of chelation treatment ( P = 0.4057). Similarly, there was a significant decrease in 24-hour UCE ( P < 0.001) during the first year of chelation treatment, then a stabilization.

Our study showed a significant decrease in ExC and 24-hour UCE levels during the first year of follow-up; The dynamics of both biomarkers were similar along the follow-up, demonstrating their usefulness in clinical practice for monitoring WD.