## **Core Concept**
The patient's symptoms of severe cognitive decline and dependence on others for basic activities of daily living, especially in the context of Down syndrome, suggest a diagnosis of Alzheimer's disease. Alzheimer's disease is characterized by specific histopathological changes in the brain.

## **Why the Correct Answer is Right**
The correct answer, , shows neuritic plaques and neurofibrillary tangles, which are hallmark histopathological features of Alzheimer's disease. Neuritic plaques are composed of amyloid-beta peptides surrounded by dystrophic neurites and microglia, while neurofibrillary tangles are intracellular aggregates of hyperphosphorylated tau protein. These features are commonly observed in the brains of individuals with Alzheimer's disease, and their presence supports the diagnosis. Individuals with Down syndrome have an increased risk of developing Alzheimer's disease, likely due to the presence of an extra copy of chromosome 21, which carries the gene for the amyloid precursor protein (APP).

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option does not show the characteristic features of Alzheimer's disease. Without a description, we can infer it's incorrect based on the context that Alzheimer's is the expected diagnosis.
* **Option B:** Similarly, this option lacks the specific histopathological features associated with Alzheimer's disease, making it an incorrect choice.
* **Option D:** This option also does not depict the hallmark features of Alzheimer's disease, thus it is incorrect.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that individuals with Down syndrome are at an increased risk of developing Alzheimer's disease, often presenting with early onset and severe cognitive decline. Screening for Alzheimer's disease in patients with Down syndrome who are over 40 years old is recommended due to this increased risk.

## **Correct Answer: .**