monomania

Pathological obsession with one idea or subject.

Intent concentration on or exaggerated enthusiasm for a single subject or idea.

Insanity in which there is a more or less complete limitation of the perverted mental action to a particular field, as a specific delusion, or an impulse to do some particular thing. The other mental functions may show some signs of degeneration.

In popular use, an unreasonable zeal for or interest in some one thing; a craze.

Synonyms Lunacy, Derangement, etc. See insanity.

Derangement of the mind in regard of a single subject only; also, such a concentration of interest upon one particular subject or train of ideas to show mental derangement.

Excessive interest or concentration on a singular object or subject.

A pathological obsession with one person, thing or idea.

a mania restricted to one thing or idea