**Correct Answer:** c) Pick's disease

**Core Concept:** Alzheimer disease is a progressive neurodegenerative disorder characterized by the accumulation of abnormal protein aggregates within neurons and in the extracellular space. Alzheimer disease is classified into three main types: early-onset familial Alzheimer disease (EOFAD), late-onset sporadic Alzheimer disease (LSAD), and Pick's disease.

**Why the Correct Answer is Right:** Pick's disease, also known as frontotemporal lobar degeneration with Pick bodies, is a distinct clinical entity that is different from Alzheimer disease. In Pick's disease, the primary pathological feature is the presence of Pick bodies, which are intracellular aggregates of the microtubule-associated protein tau. These Pick bodies are not seen in Alzheimer disease, which is characterized by the presence of extracellular senile plaques (amyloid angiopathy) and intracellular neurofibrillary tangles (composed of hyperphosphorylated tau protein). Neuritic plaques (composed of amyloid-beta protein) and Pick bodies (composed of hyperphosphorylated tau protein) are unique to Pick's disease, whereas amyloid angiopathy is a feature of both Alzheimer disease and Pick's disease.

**Why Each Wrong Option is Incorrect:**

a) Neurofibrillary tangles are a key pathological feature of Alzheimer disease, not Pick's disease.
b) Neuritic plaques are also seen in Alzheimer disease, not Pick's disease.
d) Amyloid angiopathy is present in both Alzheimer disease and Pick's disease. However, it is more prominently seen in Alzheimer disease.
e) Senile plaques are a hallmark of Alzheimer disease, not Pick's disease.

**Clinical Pearl:** The differential diagnosis between Alzheimer disease and Pick's disease is crucial as the treatment options and prognosis differ significantly. Early recognition of Pick's disease can prevent unnecessary treatment with cholinesterase inhibitors, which are used to treat Alzheimer disease but are not effective in Pick's disease.