As Tgal mentioned, none of us are doctors so we cannot give you an opinion as to what it might be. There are so many different rashes in Lupus and so many different forms of Lupus as well as over 60 different auto-immune disorders with similar symptoms. I agree with Tgal, it is important that you see your doctor about this so that you can get some type of answer and start some type of treatment. Please let us know what you and your doctors decide.
Peace and Blessings
Look For The Good and Praise It!