Q. I have been in a multiyear relationship with a 37 year old woman, diagnosed with a cluster B personality disorder who primarily expresses Borderline and Histrionic traits. Needless to say this has been difficult, high on the list of problems being the consistent lying and lack of sexual fidelity (both related). I am at a bit of a loss on two related issues. Little real-life information seems to be available.

First, how is this Cluster B expressed compared to typical written discussions on BPD behaviors? I am aware that HPD and BPD are often connected, but is this cluster B different from the "norm"? What behavior patterns can I expect from this woman? Second, Is a stable, monogamous relationship even conceivable with a person (also very attractive to men) who has this devastating personality disorder pattern. Treatment approaches?

A. To answer your question "is this cluster B different from the norm?" Cluster B is not something different from the diagnoses of HPD and BPD. HPD and BPD are part of cluster B. Please refer to the DSM for more reading on what a cluster category was used for in this manual.

Your last question centered around whether it is "conceivable" to have a stable monogamous relationship with someone with HPD and BPD. Yes, it is conceivable but takes a great deal of work. As you know, relationships are far too complex to predict based on a paragraph's worth of description. You and her need to discuss your relationship and what you both need and want in your relationship. Lying and sexual infidelity appear to be at least two areas that will require discussion. There may be other limits, needs, or boundaries that will need to be established. It may also be necessary to explore your own reasons for why you remain in the relationship as it may give you insights into what you need/want in a relationship.