A 70 yrs. old man presents with h/o prosopagnosia, loss of memory, 3rd person hallucination since 1 month On examination deep tendon reflexes are increased. Mini-mental examination score is 20/30. What is most likely diagnosis:
**Core Concept**
The patient's presentation is suggestive of a neurodegenerative disorder characterized by progressive cognitive decline, neuropsychiatric symptoms, and motor dysfunction. This condition is associated with the deposition of abnormal proteins in the brain, leading to neuronal damage and death.
**Why the Correct Answer is Right**
The patient's symptoms, including prosopagnosia (difficulty recognizing faces), loss of memory, and 3rd person hallucination, are characteristic of frontotemporal dementia (FTD). The increased deep tendon reflexes and low Mini-mental examination score further support this diagnosis. FTD is a form of dementia caused by the degeneration of the frontal and temporal lobes, which are responsible for regulating emotions, behavior, and language. The deposition of tau protein or TDP-43 in these regions leads to neuronal loss and cognitive decline.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely Alzheimer's disease, which is the most common cause of dementia. However, FTD is a more likely diagnosis given the patient's young age of onset and the presence of motor symptoms.
**Option B:** This option is likely vascular dementia, which is caused by reduced blood flow to the brain. However, the patient's symptoms are more consistent with a neurodegenerative disorder like FTD.
**Option C:** This option is likely Lewy body dementia, which is characterized by visual hallucinations and parkinsonian motor symptoms. However, the patient's cognitive decline and prosopagnosia are more consistent with FTD.
**Clinical Pearl / High-Yield Fact**
Frontotemporal dementia is a heterogeneous group of disorders, and the clinical presentation can vary depending on the specific region of the brain affected. It's essential to consider FTD in the differential diagnosis of young-onset dementia, especially in patients with prominent motor symptoms.
**Correct Answer:** C. Lewy body dementia.