Addressing rumors that have circulated about her health, Lady Gaga told CNN's Larry King this week that she doesn't have lupus, but has tested "borderline positive" for the condition. It may sound contradictory, but doctors say this can occur with lupus. Like many autoimmune diseases, lupus is a mystifying condition. It's often hard to diagnose because of its vague and varying symptoms. No two cases are alike, according to medical experts. The disease can come and go without explanation, and its severity varies from mild discomfort to death.