**Core Concept**
Wilson disease is a genetic disorder characterized by excessive accumulation of copper in the body, particularly in the liver, brain, and other organs. This accumulation leads to oxidative stress, inflammation, and cell damage. The primary goal of treatment in Wilson disease is to reduce copper levels and prevent further accumulation.

**Why the Correct Answer is Right**
Chelation therapy is a cornerstone of treatment in Wilson disease. Penicillamine is a copper-chelating agent that binds to free copper ions in the body, facilitating their excretion through urine. This process helps to reduce the accumulation of copper in organs and tissues. Penicillamine works by forming a complex with copper ions, which are then excreted by the kidneys.

**Why Each Wrong Option is Incorrect**
**Option A:** Deferoxamine is a chelating agent used primarily for iron overload, not copper accumulation.
**Option B:** Succimer is a chelating agent used for lead poisoning, not Wilson disease.
**Option C:** Dimercaprol is a chelating agent used for arsenic, mercury, and lead poisoning, not copper accumulation.

**Clinical Pearl / High-Yield Fact**
Chelation therapy should be initiated under close medical supervision, as it can cause side effects such as skin rashes, joint pain, and kidney damage. Regular monitoring of liver function and copper levels is essential to ensure the safe and effective use of chelating agents.

**Correct Answer: D. Penicillamine**