Karp's specialty is lupus, which affects 1.5 million Americans, according to the Lupus Foundation of America. Lupus can be mild, as in Tota's case, or it can be severe, leading to kidney failure and death. But the blood tests used to diagnose lupus can confuse primary-care physicians, Karp says. "I probably undiagnose as many people as I diagnose."
Source: wiktionary