22 Hard-To-Detect Illnesses, From The Commonplace To The Truly Bizarre

18. Cotard’s Delusion

Also known as walking corpse syndrome, Cotard’s delusion is an extremely rare mental disorder in which the afflicted person believes that they are already dead, or that their body is putrefying in a post-death state. Named for 1880s neurologist Jules Cotard, this psychological affliction can vary greatly in severity, with some sufferers only experiencing mild levels of despair, while others go through periods of intense delusion and chronic depression.