## Core Concept
Huntington's chorea, also known as Huntington's disease, is a progressive brain disorder caused by a genetic defect on chromosome 4, leading to physical, cognitive, and psychiatric problems. The disease is characterized by **involuntary movements (chorea), psychiatric problems, and cognitive decline**. The underlying pathophysiology involves degeneration of neurons in the **basal ganglia**, particularly the caudate nucleus.

## Why the Correct Answer is Right
The correct answer involves understanding the typical features and neuropathological changes in Huntington's disease. The disease is associated with **atrophy of the caudate nucleus and putamen**, which are parts of the basal ganglia. This atrophy leads to the characteristic motor symptoms, including chorea. **Dopamine receptor density is decreased** in the striatum (which includes the caudate nucleus and putamen) due to the degeneration of neurons that express these receptors.

## Why Each Wrong Option is Incorrect
- **Option A:** Not specified, but if related to common findings in Huntington's, such as chorea or cognitive decline, it would be correct and not the answer.
- **Option B:** Similarly, without specifics, if it's a common feature like psychiatric symptoms or motor dysfunction, it would align with Huntington's manifestations.
- **Option C:** If this option relates to decreased dopamine receptor density or another neuropathological feature consistent with Huntington's, it would be a characteristic finding.
- **Option D:** This option is stated as the correct answer, implying it is **not typically found in Huntington's chorea**. If it suggests an **increase in dopamine receptor density**, this would be incorrect in the context of Huntington's disease, where there's a degeneration of neurons leading to a decrease, not an increase.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that Huntington's disease is an **autosomal dominant disorder**, meaning a mutation in one of the two copies of the gene is sufficient to cause the condition. This leads to a significant risk of passing the disease to offspring. Another important point is the **association with psychiatric symptoms** and **cognitive decline**, alongside the more recognizable motor symptoms.

## Correct Answer: D. Increased dopamine receptor density.