1. Philadelphia Veterans Affairs Medical Center; Philadelphia PA U.S.A.
2. Department of Dermatology; University of Pennsylvania School of Medicine; Philadelphia PA U.S.A.
3. Division of Immunology and Rheumatology; Department of Dermatology and Medicine; Stanford University School of Medicine; Stanford CA U.S.A.
4. Department of Biostatistics and Epidemiology; University of Pennsylvania; Philadelphia PA U.S.A.