Some years ago, I remember reading Jonathan Kellerman's Savage Spawn, a book on sociopathic children, and how nearly impossible it is to treat them.  The other day I heard about someone I know who is apparently going through this with their child, which prompted me to search for the term.  It's truly heartbreaking:  a child who doesn't seem capable of loving its parents, or anyone else.  It seems to be mostly genetic, and nearly completely immune to any current treaments.  I thought the story of the woman who inspired The Changeling was the most heartbreaking thing I had read in a while, but I wonder if there aren't worse ways to lose a child.