Why is it so difficult for physicians to find a cure for immune diseases like Lupus?

Because the immune system is made to adapt. When it misfires as it does in auto immune diseases it kills both healthy and normal cells. So far gene therapy trying to cure lupus has been unsuccessful because the immune system adapts again and attacks the new gene. It has been very frustrating for researchers and is a very difficult task. Remember, no one has found a cure for the common cold and this is a much simpler task than trying to reboot the entire immune system. We like to think that we are extremely technologically advanced but we are still at the mercy of the tiniest critters in the world.