This may not be the answer you are looking for, but this is way beyond what the MCAT will ask you. You don't need to know about disease states or pathophysiology at all--as long as you have a handle on basic science concepts, you will be totally fine. If the MCAT were to ask you something about polyarthritis, it would have detailed the disease in a passage, and everything that you would need to know would be found in the passage.
