I've brushed up on different psychiatric conditions with Medline Plus (and Wikipedia), but my character's "symptoms" are just a single, extremely detailed & consistent monothematic delusion + total amnesia when it comes to his "real" life. He communicates coherently, doesn't exhibit odd behaviors, and, while depressed and anxious for obvious reasons, doesn't have anything resembling a mood disorder. He's been screened for trauma or disease that might cause amnesia or psychosis as a secondary symptom. Before this happened, he was in good physical and mental health.
So, when he's forced to visit a psychiatrist, how might she diagnose him? Delusional disorder? A fugue state (even though he hasn't wandered off from home)? Can you be diagnosed with a monothematic delusion independently of any umbrella disorder?
It has occurred to me that, since his story is so pat, she might suspect he's faking it - in which case she might attribute it to a personality disorder.
Thanks to everyone for any help you can offer (and happy New Year!)
ETA: He is magically speaking modern "English" (not really English in this world). His speech is formal but not archaic.
