## **Core Concept**
Wilson's disease, also known as hepatolenticular degeneration, is a rare genetic disorder characterized by excessive accumulation of copper in the body, particularly in the liver, brain, and other vital organs. This condition is caused by mutations in the **ATP7B gene**, which plays a crucial role in regulating copper transport and excretion. The diagnosis involves a combination of clinical evaluation, laboratory tests, and genetic analysis.

## **Why the Correct Answer is Right**
The correct answer involves the diagnostic method that directly assesses the level of a specific protein or genetic mutation associated with Wilson's disease. **Sequencing of the ATP7B gene** is considered the gold standard for diagnosing Wilson's disease as it can identify mutations in the gene that are responsible for the condition. This genetic test can confirm the diagnosis and help in family screening.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although liver biopsy can show copper accumulation, it is not the most specific or sensitive method for diagnosing Wilson's disease.
- **Option B:** This option is incorrect because, while measuring **ceruloplasmin levels** (the protein that carries copper in the blood) can support the diagnosis (as levels are often low in Wilson's disease), it is not definitive on its own due to the possibility of other conditions affecting ceruloplasmin levels.
- **Option D:** This option is incorrect because **slit-lamp examination** can reveal Kayser-Fleischer rings (copper deposits in the cornea), a sign suggestive of Wilson's disease, but it is not diagnostic on its own.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Wilson's disease is one of the few conditions where **penicillamine** or **zinc acetate** can be used as specific treatments to reduce copper accumulation. Early diagnosis and treatment are crucial to prevent irreversible organ damage.

## **Correct Answer:** . **Sequencing of the ATP7B gene**