This video answers the question: How can we differentiate autism spectrum disorder from personality disorders? Specifically, when I talk about autism spectrum disorder, I'm referring to the high-functioning end of the autism spectrum and a presentation that doesn't have intellectual impairment. When we talk about autism spectrum disorder, we know that this particular type of presentation is often diagnosed late in life, it's often misdiagnosed, and a lot of the time it's confused with personality disorders. Autism spectrum disorder and personality disorders share a few different things in common and one of those features is they're both ego-syntonic, which means that there's a lack of insight it.
Autism spectrum disorder is listed in the Diagnostic and Statistical Manual (DSM) and here we see this disorder is characterized by deficits in social communication and social interaction as well as restrictive, repetitive patterns of behavior, interest, and activities. Borderline Personality Disorder and Narcissistic Personality Disorder are both Cluster B Personality Disorder. With BPD we see a pattern of unstable relationships, unstable mood, impulsivity, identity disturbance, anger, a chronic feeling of emptiness, and we also see an increased risk of suicidal ideation, gestures, threats, and other behaviors. NPD characteristics like being arrogant, jealous, having a lack of empathy, requiring excessive admiration, tending to manipulate people, and having a sense of entitlement.
Dudas, R. B., Lovejoy, C., Cassidy, S., Allison, C., Smith, P., & Baron-Cohen, S. (2017). The overlap between autistic spectrum conditions and borderline personality disorder. PLoS ONE, 12(9), 1–13.
Strunz, S., Westphal, L., Ritter, K., Heuser, I., Dziobek, I., & Roepke, S. (2015). Personality Pathology of Adults With Autism Spectrum Disorder Without Accompanying Intellectual Impairment in Comparison to Adults With Personality Disorders. Journal of Autism and Developmental Disorders, 45(12), 4026–4038.