From the people I have seen who seem to have this type of problem, they were brought up by parents who gave feedback along the line of making the child think he was special and superior, and the child believed it.
He was abandoned first by his Dad, then by his Mom, bounced between Hawaii, Kenyan & Chicago. He was forcd to adapt to wildly different cultures, raised by a young single college student, older grandmother and marxist stepfather. Throw communist Frank Davis into the mix, college misfits and twenty years of Reverend Wright hate, and you have a pretty toxic environment.