## Why "Mutation in ATP7B gene on chromosome 13q14 impairing biliary copper excretion and ceruloplasmin loading" is right Wilson disease is an autosomal recessive disorder caused by mutations in the ATP7B gene (chromosome 13q14), which encodes a copper-transporting ATPase essential for biliary copper excretion and incorporation of copper into ceruloplasmin. When ATP7B is defective, copper cannot be excreted into bile or loaded onto ceruloplasmin, causing pathological accumulation in the liver (visible as rhodanine-positive granules on biopsy). The clinical presentation—fulminant hepatic failure with Coombs-negative hemolytic anemia, low ceruloplasmin, and copper-laden hepatocytes—is pathognomonic for Wilson disease. This patient's age (24 years), acute presentation, and hepatic crisis with hemolytic anemia are characteristic of Wilson disease in young women (Robbins 10e Ch 18; Harrison 21e Ch 408). ## Why each distractor is wrong - **Defective hepatic synthesis of metallothionein leading to impaired intracellular copper binding**: Metallothionein is a copper-binding protein, but its deficiency is not the primary genetic defect in Wilson disease. ATP7B dysfunction is the root cause, not metallothionein synthesis. Zinc acetate therapy works by *inducing* metallothionein, but this is a treatment strategy, not the disease mechanism. - **Autosomal dominant mutation in the copper transporter gene CTR1 causing excessive intestinal copper absorption**: Wilson disease is autosomal *recessive*, not dominant. CTR1 mutations are not the cause of Wilson disease; ATP7B is the culprit gene. Excessive intestinal absorption is not the primary pathophysiology—the problem is hepatic excretion and ceruloplasmin loading. - **Acquired ceruloplasmin deficiency secondary to severe malnutrition and cirrhosis**: While ceruloplasmin is low in Wilson disease, this is a *consequence* of ATP7B dysfunction (inability to load copper onto ceruloplasmin), not a primary acquired deficiency from malnutrition. The low ceruloplasmin is secondary to the genetic defect, not the cause of copper accumulation. **High-Yield:** Wilson disease = ATP7B mutation → impaired biliary copper excretion + failed ceruloplasmin loading → hepatic copper accumulation (rhodanine-positive on biopsy) + spillover to brain, cornea, kidney; fulminant hepatitis + Coombs-negative hemolytic anemia in young women is a red flag. [cite: Robbins 10e Ch 18; Harrison 21e Ch 408]
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