Reference intervals of spot urine copper excretion in preschool children and potential application in pre-symptomatic screening of Wilson disease

A Reaction-based Ratiometric Fluorescent Probe with Large STOKES Shift for Cu2+ in Neat Aqueous Solution

A novel reaction-based ratiometric fluorescent probe 1 for Cu2+ using picolinate as the reaction site and hemicyanine as the fluorophore was developed. 1 displayed maximum absorption peak at 355 nm and fluorescence emission peak at 500 nm, with large Stokes shift of 145 nm. Upon reaction with Cu2+, the maximum absorption and fluorescence emission peaks red-shifted to 390 nm and 570 nm respectively, owing to Cu2+-induced hydrolysis of the picolinate moiety in 1. Meanwhile, the solution of 1 turned from green to orange under a 365 nm UV lamp. 1 not only could detect Cu2+ ratiometrically by the ratios of both absorbance (A390 nm/A355 nm) and fluorescence intensity (F570 nm/F500 nm), but also displayed large Stokes shift, fast response, high sensitivity and excellent selectivity over other metal ions in neat aqueous solution.

Wilson disease in children and young adults - State of the art

Wilson disease (WD) is an autosomal recessive disorder caused by mutations of the ATP7B gene, with a reported prevalence of 1:30,000-50,000. ATP7B encodes an enzyme called transmembrane copper-transporting ATPase, which is essential for copper incorporation into ceruloplasmin and for copper excretion into the bile. A lack or dysfunction of this enzyme results in a progressive accumulation of copper in several organs, especially in the liver, the nervous system, corneas, kidneys, and heart. Children with WD can present with asymptomatic liver disease, cirrhosis, or acute liver failure, with or without neurological and psychiatric symptoms. Approximately 20%-30% of WD patients present with ALF, while most of the other patients have chronic progressive hepatitis or cirrhosis if untreated. Although genetic testing has become a more important diagnostic tool for WD, the diagnosis remains based on both clinical features and laboratory investigations. The aims of treatment are to reduce copper levels and prevent its accumulation in the liver and other organs, especially in the central nervous system. Liver transplantation in WD is a life-saving option for patients presenting with liver failure and encephalopathy. For WD patients treated with chelating agents, adherence to the therapy is essential for long-term success. In this review, we also address specific issues in young adults as compared to children.

Long-Term Urinary Copper Excretion on Chelation Therapy in Children with Wilson Disease

OBJECTIVES

In Wilson disease (WD), 24-hour urinary copper excretion (UCE) is recommended to be used for diagnosis. It may be a useful tool to assess the efficacy of treatment during follow-up; however, there are limited data regarding the cutoff value of 24-hour UCE during follow-up in children. Therefore, we aim to evaluate the clinical use of 24-hour UCE during follow-up in children with WD.

PATIENTS AND METHODS

Medical records of children diagnosed with WD at Kings' College Hospital from 2005 to 2018 were retrospectively reviewed. The UCE, serum copper, and ceruloplasmin levels, tested during follow-up, were statistically analyzed.

RESULTS

Over the median duration of 7 years (range 1.4-14.4), 28 patients (age ranged 3.8-17.3 years) had UCE tests during follow-up. Of those, 21 patients had at least one 24-hour UCE test and 7 children had only spot UCE tests. In comparison with the level of 24-hour UCE collected at the first visit after penicillamine challenge test, the median excretion rate was significantly reduced over the follow-up period (P < 0.001), from 26.2 to 8.9 μmol/day following 1-2 years of therapy (P = 0.15), then reduced significantly to 2.2 μmol/day after 3-4 years (P = 0.009), and 5.6 μmol/day at >5 years of follow-up (P = 0.003).

CONCLUSIONS

Our study suggests that within 1 year of treatment, the level of nonceruloplasmin-bound copper concentration (NCC) drops to <0.8 μmol/L. In the absence of progressive liver disease or signs of copper deficiency, 24-hour UCE decreases to ≤8 μmol/day and <6 μmol/day after 1 and 5 years of treatment, respectively.