My father had Capgras Syndrome the last 18 months of his life as he struggled with ALZ, and it was quite a challenge. As @organist1 mentioned, considerably different than prosopagnasia. Capgras seems mostly to affect one person the victim knows, usually that being closest to them, even if it's a pet.

I knew huge areas of the brain heat up when viewing faces of other animals not just humans....with any biochemical function, there are likely mutations and dietary deficiencies/injuries....thankyou for linking these 2 and primal FACEBOOK

. . . and fairly unconvincing of "understanding Facebook" !

I think my earlier post could enlighten some FB users :

"Do y'all FB (AOL,Yahoo!) users think you are critical thinkers and have a nose-for-news ?"

I have read about Capgras Syndrome before. There have been some attempts to treat it with Oxytocin, which have been successful, to some extent. Capgras is more than just prosopagnosia, because while a person with face blindness doesn't recognize a person by sight, once they know who the person is, they accept who the person is, and feel the connection. The late neurologist Oliver Sacks, who was face blind, wrote extensively about it.