Michael Jackson, skin disease?

My sister-in-law just said that Michael Jackson's skin turned white because he had a skin disease. I've never heard that before? Is it true? Or is it a lie/ cover up? I'm not a fan of his, i'm really impartial to him. I don't hate him either. But I was just wondering, has anyone else heard this? And if so, is it true? It sounds like something they may have made up after his death, but that's just me...