Psychiatrymiddle twist
A 74-year-old man is brought by his wife because for the past year he has described the small children who come into the lounge room most afternoons; he can say what they are wearing, is not frightened by them and accepts that she cannot see them. Some days he is bright and conversational, on others he sits staring and can barely be roused for hours. His handwriting has become tiny, he shuffles and he has fallen twice. His memory is only mildly affected. There is no infection, dehydration or new medication. Which one of the following is the most likely diagnosis?