This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
User has found an issue in which Anim Notifies, spawning particle system components that cannot ever render will leak the particle system component.
The user has a working fix but it's likely not ideal.
Investigate a more permanent fix.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-18991 in the post.