ATP7B is a gene encoding a copper‑transporting P‑type ATPase; its protein regulates copper incorporation into ceruloplasmin and biliary copper excretion. Mutations cause loss of ATP7B function, leading to impaired hepatic copper export and toxic copper accumulation in liver, brain, and cornea, producing the clinical features of Wilson disease. The disorder is autosomal recessive and severity varies with mutation type.

Testing for ATP7B involves targeted genetic analysis: sequence the ATP7B gene using next-generation or Sanger sequencing to identify pathogenic variants, with deletion/duplication testing if suspicion remains. Clinical workup includes serum ceruloplasmin, 24‑hour urinary copper, slit‑lamp exam for Kayser‑Fleischer rings and, if needed, hepatic copper quantification via liver biopsy. Genetic counseling is recommended for patients and relatives.

ATP7B is a liver-expressed copper-transporting P-type ATPase that regulates systemic copper homeostasis by loading copper onto ceruloplasmin and exporting excess copper into bile for excretion. It redistributes within hepatocytes according to copper levels and prevents toxic accumulation; loss-of-function mutations impair biliary excretion and ceruloplasmin incorporation, causing copper buildup and related disease.

The ATP7B test is genetic testing that detects mutations in the ATP7B gene—commonly called ATP7B gene sequencing or ATP7B mutation analysis. It is used to confirm or exclude Wilson disease (a disorder of copper metabolism) and may be performed as a single-gene test or within a hereditary liver disease panel. Results guide diagnosis, family screening, and management.

ATP7B is predominantly expressed in hepatocytes in the liver, where it normally resides in the trans‑Golgi network and traffics to biliary canalicular membranes to export excess copper. It is also expressed at lower levels in the brain (neurons and glia), kidney, placenta and some other tissues, where it helps regulate local copper distribution and prevent toxic accumulation.

Wilson's disease is confirmed by a combination of clinical features and specific tests: low serum ceruloplasmin, Kayser–Fleischer rings on slit‑lamp exam, elevated 24‑hour urinary copper excretion, and increased hepatic copper concentration on liver biopsy (typically >250 µg/g dry weight). Identification of pathogenic ATP7B mutations on genetic testing further supports or confirms the diagnosis.