Augustus "Little Augie" Aprile is a mob figure well known enough for Dr. Elliot Kupferberg to assume that Dr. Melfi was treating him when her real patient was Tony Soprano. He is an Unseen Character referenced in "Employee of the Month".
It is not known whether he was a paternal relative of Jackie Aprile, Sr. or a member of the DiMeo/Soprano crime family. Because Dr. Melfi is a psychiatrist, it is assumed by the inquiry by Dr. Kupferberg that Augustus Aprile either is known to demonstrate psychotic behavior or anger management issues for needing to actually see a psychiatrist. Then again, it could just be that Dr. Kupferberg is confusing names, and that there is no such character.