Differential Diagnosis

The patient's presentation of sudden withdrawal, forgetfulness, difficulty with word-finding, and inappropriate behavior such as being found naked and urinating in the room suggests a significant cognitive and behavioral decline. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Frontotemporal Dementia (C): This condition is characterized by changes in personality, behavior, and language due to degeneration of the frontal and temporal lobes of the brain. The patient's sudden withdrawal, difficulty with word-finding (aphasia), and socially inappropriate behavior (being naked and urinating in the room) are classic symptoms of frontotemporal dementia, particularly the behavioral variant.

• Other Likely Diagnoses

  • Vascular Dementia (B): Given the patient's history of hypertension and smoking, vascular dementia is a consideration. It typically presents with a step-wise decline in cognitive function, but the patient's behavioral changes and language difficulties could also fit this diagnosis.
  • Alzheimer's Disease (D): While Alzheimer's is the most common cause of dementia, the patient's presentation with prominent behavioral changes and language difficulties early in the course is less typical for Alzheimer's, which usually starts with memory complaints.
  • Lewy Body Disease (E): Characterized by fluctuations in cognitive function, visual hallucinations, and parkinsonian motor symptoms, Lewy body dementia could be considered, especially if the patient has significant variability in his alertness and cognitive function throughout the day.

• Do Not Miss Diagnoses

  • Depression (A): Although depression can cause significant cognitive impairment, especially in the elderly (pseudodementia), the patient's behavioral changes and specific cognitive deficits (like aphasia) are less typical for depression alone. However, depression can coexist with or mimic dementia, and missing it could lead to inadequate treatment.
  • Delirium: An acute and fluctuating disturbance of consciousness and cognition, delirium can present with similar behavioral disturbances and should always be considered, especially if there's an identifiable precipitant like infection, medication change, or other medical conditions.

• Rare Diagnoses

  • Prion Diseases: Such as Creutzfeldt-Jakob disease, which can present with rapid cognitive decline, behavioral changes, and myoclonus. It's rare but important to consider due to its fatal prognosis and the need for prompt diagnosis.
  • Normal Pressure Hydrocephalus (NPH): Characterized by the triad of gait disturbance, dementia, and urinary incontinence. While the patient's urinating in the room could suggest NPH, the prominent language and behavioral changes are less typical, making this a less likely but not impossible diagnosis.