**Question:** The following is not a feature of Alzheimer's disease

A. **Increased risk of infections**
B. **Improved cognitive function with dopaminergic medications**
C. **Normal variation in cognitive function**
D. **Absence of extracellular amyloid plaques and intracellular neurofibrillary tangles**

**Core Concept:** Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by extracellular amyloid plaques and intracellular neurofibrillary tangles. Clinical manifestations include cognitive decline, memory loss, and behavioral disturbances.

**Why the Correct Answer is Right:** The correct answer, **D** (absence of extracellular amyloid plaques and intracellular neurofibrillary tangles), is right because these pathological features are specific to Alzheimer's disease and do not represent a non-specific feature of the condition.

**Why Each Wrong Option is Incorrect:**

A. **Increased risk of infections:** Infections can exacerbate Alzheimer's disease symptoms, but they are not a defining feature of the condition.

B. **Improved cognitive function with dopaminergic medications:** Dopaminergic medications are typically used to treat Parkinson's disease, not Alzheimer's disease. Although patients with both diseases may experience cognitive improvement due to medication side effects, this option is incorrect because it does not reflect the disease itself.

C. **Normal variation in cognitive function:** Alzheimer's disease is characterized by progressive cognitive decline, not normal variation. This option is incorrect as it does not address the pathological features of the disease.

**Clinical Pearl:** Extracellular amyloid plaques and intracellular neurofibrillary tangles are the hallmark features of Alzheimer's disease. These pathologies are not present in other neurological conditions and serve as valuable diagnostic criteria for Alzheimer's disease.