firstly,the sister condition to shy bowel syndrome is shy bladder syndrome. the other name for shy bladder is Avoidant Paruresis. Why avoidant? Because people end up avoiding a lot of situations and social settings (and of course avoiding public toilets).
Perhaps parcopresis should really be termed in the same way: Avoidant Parcopresis, since shy bowel sufferers avoid a lot of situations and social settings.
Kinda gives support for your idea about Avoidant Personality Disorder. People with this condition almost always behaving in an avoidant way.
Second thing is that i've done a bit more research on PD's generally, and I came across 'Mixed Personality Disorder'. i.e. a person's PD might be a mix of 2 or more distinct PD's. Which kinda makes sense as well. Life is messy. We don't all fit into neat little classification boxes. Certainly, I feel that may be the case with me: that i might have a mix of BPD and AvPD.
Anybody else relate to this Personality Disorder thing?