Borderline Personality Disorder (BPD) By Mark Zimmerman, MD, Rhode Island Hospital Reviewed / Revised May 2021 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Treatment More Information Borderline personality disorder is characterized by a pervasive pattern of instability and hypersensitivity in interpersonal relationships, instability in self-image, extreme mood fluctuations, and impulsivity.