A Google search gives a range of good contributions on BPD.
One of the problems of a diagnostic concept of "personality disorders" is that it appears to try to locate within the individual as almost a disease what is better discussed as a problem of *inter* personal relations. That is less judgemental and blends with ordinary expeience that we all have situations or people which we find difficult to handle.
In a loose way I think the concept of personality disorders is linked with capitalist ideology: the fiction that we are all atomised indiduals coming together to buy or sell our labour power or the products of labour. Someone with a "personality disorder" is of inferior quality, but might in a larger social setting, play a pivotal social role, such as president of the USA or member of the British Royal Family, to take just two examples.
Generally the disease model is more problematic in mental health than the syndrome or symptom model.
Chris Burford