Off Treatment Urinary Copper Excretion in Wilson Disease, Pilot Study

Inclusion Criteria: * Patients with Wilson Disease as defined by Leipzig score ≥4. * Provision of signed and dated informed consent form. * Stated willingness to comply with all study procedures (serial 24 h urine collections and local collection of samples for NCC, liver function and estimated GFR) and availability for the duration of the study. * Treated WD for at least 12 months prior to study entry. * Aminotransferase values (ASAT and ALAT) \< 2 times the upper limit of normal (ULN). * INR \< 1.5 or stable INR for those with initial elevated INR for at least six months prior to study entry in the absence of anticoagulation therapy. * Renal function defined as eGFR \> 30 cc/min. * No change of WD therapy during the previous 6 months of study enrollment. Exclusion Criteria: * Current dual / mixed therapy for WD (i.e. zinc and d-penicillamine or trientine at the same time) * Current Pregnancy or lactation. \* * Recent estrogen-based treatment (in the last month). * Cirrhosis with recent hepatic decompensation (within the last 6 months) - new onset of ascites, spontaneous bacterial peritonitis, esophageal variceal bleeding, or hepatic encephalopathy * Investigator believes the patient will be unable to do the required 24-hour urine studies and participate in the follow up visits as expected. * Previous non-compliance for therapy and/or to low-copper diet that would compromise the evaluation of previous UCE and/ or results from the off-treatment period. * Childbearing aged patients recruited outside of the registry will be reviewed, and the patients will be asked to perform an initial urine pregnancy test prior to the recommended blood testing (approximately 60 to 90 days prior to intervention). They will be permitted to continue with the screening process if the result is negative. They will be asked to perform a second urine pregnancy test as close as possible prior to study intervention (discontinuation of treatment). If the result of the second pregnancy test is negative they will be permitted to continue with the protocol, but if the result is positive they will be excluded from further participation at that time. Childbearing aged patients recruited from the registry who meet inclusion criteria and may move directly to the study intervention will be required to perform a urine pregnancy test as close as possible to the time prior to the initiation of the study protocol (discontinuation of treatment).