Sex With Ghosts - Possible Clinical Diagnoses Spectrophilia, is described by Wikipedia as the sexual attraction to ghosts or sexual arousal from images in mirrors, as well as the phenomenon of sexual encounters between ghosts and humans.
A quick and easy search shows us that many people claim to have had these encounters, and seem completely convinced of their experiences.
Question:
If someone walked into a psychiatrists office with these claims, (assuming they are seemingly normal otherwise, and have no history of mental illness), what would they most likely be diagnosed with? And what medicine might they be prescribed?

Things we're assuming to be true:
Ghosts aren't real.
Sleep paralysis can sometimes result in hallucinations corollary to the paralysis experience. Similarly, bipolar I and other psychotic disorders (viz. the schizophrenia spectrum) could produce vivid enough hallucinations and delusions, though in general, vivid visual hallucinations are quite rare.

It is highly unlikely that someone who is describing these experiences is not experiencing any other symptoms. 

Standard treatment would depend primarily on what other issues the patient might be experiencing. 

If the patient is experiencing dissociation and misinterpreting this as sex with ghosts for some reason, cognitive or dialectical behavior therapy would be the indicated treatment.

If the patient were agitated, or disoriented to time, place, or person, the psychiatrist would likely prescribe psychotherapy and an atypical antipsychotic (e.g. risperidone, brexipiprazole).

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Sharpless, Brian A., et al., Journal of Clinical Psychology, 2010; vol 66: pp 1292-1306.

Bell, CC, et al., " American J Psychiatry, 1986; vol 143: p 1484.

Ranier Biobehavioral Institute: "Sleep Paralysis."

Mayo Clinic. "Dissociative Disorders."