A 70 yr old man presents with h/o prosopagnosia

A 70 yr old man presents with h/o prosopagnosia, loss of memory, 3rd person hallucination since 1 month. On examination deep Tendon reflexes are increased, minimental examination score is 20/30. What is most likely diagnosis -

a.Dissociated dementia
b.Schizophrenia
c.alzheimers disease
d.Psychotic disorder

ans:
Similar to previous question a low MMSE score suggests cognitive impairment, e.g. Dementia.
Prosopagnosia, loss of memory and low MMSE score suggest the diagnosis of Alzheimer’s disease.
Only confusion in this question is third person hallucination. Third person hallucination is characteristic of schizophrenia. However, schizophrenia can be excluded, because MMSE score is not low in schizophrenia.