http://en.wikipedia.org/wiki/Lupus_erythematosus

And here's the WebMD link: http://www.webmd.com/content/article/6/1680_51584.htm

The big thing to understand is that we don't know a whole lot about lupus. We know what causes it (it's an autoimmune disease) but we don't know why those auto antibodies develop. Just to explain: An antibody is a molecule that binds to "foreign" material so that the immune system can recognize it and get rid of it. An autoimmune disease is a disease where the body makes antibodies that attack normal parts of the body instead of the "foreign" molecules. AIDS is another well-known example of an autoimmune disease, because the HIV virus tricks the immune system into attacking itself.

The reason we kept hearing about Dilla's "kidney" problems is that the kidneys are the biggest indicator of how severe an individual's affliction with lupus is.

I'm more than happy to answer any questions that anyone has. I'll try to keep as much 'medical lingo' out as I can or at least explain the terms I do use.