NUP is a form of periodontitis that is caused by similar agents to NUG, which are bacterial infections such as Treponema, Selenomonas, and Fusobacterium nucleatum. While NUG only involves gingivitis, NUP is distinguished by clinical attachment and bone loss. Recent reviews suggest that NUP and NUG are clinical manifestations of the same disease, except NUP features more severe periodontal tissue destruction.