With medical conditions:
* The surgery was riskier due to the patient's preexisting heart condition.
* The insurance company denied coverage for the treatment, claiming it was related to a preexisting condition.
With other situations:
* The new policy built upon the preexisting framework of the old one.
* The band's preexisting fanbase eagerly awaited the release of their new album.
* The museum curator discovered a preexisting inscription on the ancient artifact.
In a figurative sense:
* The team's preexisting rivalry fueled their competitive spirit.
* His preexisting distrust of politicians made him skeptical of the new campaign promises.
Remember that "preexisting" implies something that existed before a specific event or situation.