I think that we can safely say that Mr. Jackson was not human. (Yes, hence the antennae).
To start off with– he pioneered the MOON walk!! That should be a hefty hint, shouldn’t it?
Though his skin may have had a disease that resulted in non-pigmentation, it’s rumored that his skin was flakey– clearly this alien that was living within him hadn’t quite mastered the art of Humaning, as humans tend to not fall apart.
And now you’re wondering– alien living INSIDE of him?
But of course!
Remember in Men In Black how there was a little alien dude living in place of the brain of someone killed by the Parasite? Same deal here. Though we know his nose was heavily plastic surgerie’d, (or so the story goes), consider the fact that his nose had a tendency of falling apart/off towards the end of his days. Yes, there were slits of nostril that went into his face, but consider: would an alien need oxygen? Likely not, as there is far from any abundance of it out there with the stars. Given this, said alien lived in the cavity that his lungs WOULD have occupied, had he been human.
As a kid, the alien was best able to keep on the human-look, but as his human skin aged, away aged his covering and it fell off and apart, revealing the strange alien-eyed, wide-chinned creature we all know better as Michael Jackson.
How I wish he would have lived to be eighty. I really wonder what he would have looked like by then.