Well there has got to be a solution as he is oblivious to the disruptions he causes in our department, particularly to his manager and to me as his go-to guy on every personal matter of his under the Sun.

So if I follow your lead and we continue to take it lying down it will continue to fester until the next blowup he sparks. Maybe then the only solution will be to force someone to leave the department or the company.

After all, it's treatable, correct? So why wouldn't it be somebody's place to help him and in the process help those around him?

The passive, do-nothing approach has been tried for too long here and it does not work for anybody.