Wilson disease is caused by a mutation that prevents copper excretion from the liver, leading to copper accumulation and damage to tissues like the basal ganglia and cornea. Symptoms include liver problems like hepatitis or cirrhosis as well as neurological issues like parkinsonism or psychiatric changes. Diagnosis involves testing for low ceruloplasmin and high urinary copper as well as examining the eyes for copper rings and testing liver copper levels. Treatment uses copper chelators like penicillamine or zinc to interfere with copper absorption.