I struggled with understanding the difference between these two also. I have been told repeatedly that I have BP - but then about 2 years ago my therapist suggested I also have BPD. Well, that was new information which I rebelled against. I thought I was defined, now I had something new!

This is what I understood about the 2.

1. BP just comes out on its own.
2. BPD is caused by something happening.

1. BP can be helped with medication - talk therapy may or may not be needed depending on person.
2. BPD - talk therapy, and DBT are common treatments - drugs are not mandatory although common.

1. BP is something that a person could conceivably have their entire life - it is a brain thing.
2. BPD can be gotten over with time and therapy.

I am not a Dr. This is my understanding of some of the differences.