Capgras syndrome: uncommon syndrome in which a patient has a delusional belief that a person, usually a family member or friend, has been replaced by an imposter.
French psychiatrist, Jean Marie Joseph Capgras (1873-1950) best known for his description 'syndrome d’illusion des sosies', Capgras syndrome in 1923
Jules Cotard (1840 - 1889) was a French neurologist and psychiatrist. Délire de négations - Cotard Syndrome (1882)
Cotard syndrome: A rare condition characterized by nihilistic delusions, where a patient believes that they are dead, have missing organs, or have decaying or failing body parts.