## **Core Concept**
Lewy bodies are abnormal protein clumps that are a hallmark of certain neurodegenerative diseases. They are primarily composed of **alpha-synuclein**, a protein that plays a critical role in the pathogenesis of these conditions. The presence of Lewy bodies is a key diagnostic feature in the neuropathological examination of brains affected by specific neurodegenerative disorders.

## **Why the Correct Answer is Right**
The correct answer, **D. Parkinson's disease**, is right because Lewy bodies are a characteristic neuropathological feature of Parkinson's disease (PD). PD is a progressive neurodegenerative disorder that primarily affects movement. The Lewy bodies in PD are composed of **alpha-synuclein**, **ubiquitin**, and other proteins. These inclusions are found in the **substantia nigra** and other areas of the brain, and their presence is a key diagnostic criterion for PD.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Alzheimer's disease is characterized by the presence of **amyloid plaques** and **neurofibrillary tangles**, not Lewy bodies. While some patients with Alzheimer's disease may also have Lewy bodies (in the context of dementia with Lewy bodies), the primary association is not with Alzheimer's disease.
- **Option B:** Huntington's disease is characterized by **atrophy of the basal ganglia** and the presence of **polyglutamine-expanded huntingtin protein** in the form of inclusions. Lewy bodies are not a characteristic feature of Huntington's disease.
- **Option C:** Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of **motor neurons** and the presence of **TDP-43**-positive inclusions, not Lewy bodies.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **dementia with Lewy bodies (DLB)** is a condition that shares features with both Alzheimer's disease and Parkinson's disease. DLB patients often present with **fluctuating cognitive impairment**, **visual hallucinations**, and **parkinsonian motor symptoms**. The presence of Lewy bodies in the cortex is a diagnostic hallmark of DLB.

## **Correct Answer:** D. Parkinson's disease.