I have no idea how this is on Hacker News, but Capgras is both fascinating and tragic. The tragedy is when a family member is alienated as a result. The patients that I have worked with who had Capgras due to dementia have sometimes had this delusion in relative isolation to other changes, whereas the patients I have seen who had it due to schizophrenia often had a variety of related and unrelated delusions.
Sadly, when it is related to dementia it usually doesn't clear. When it is related to schizophrenia, it often clears in days to weeks with medication.