Mondo Description A rare neuropsychiatric disorder whose primary feature is the delusion that relatives or close acquaintances are not the persons that they are known to be. Visual recognition appears intact but familiar persons are thought be imposters, that is, they appear similar or identical to known individuals but are not. Most cases are seen in the context of a psychotic state. However, if manifested post-traumatically, the cause is most likely due to neurologic impairment. This disorder should be contrasted with prosopagnosia, in which an individual may not recognize a familiar person at all.