[1] Univ Penn, Sch Med, Dept Dermatol, Perelman Ctr Adv Med, Philadelphia, PA 19104 USA
[2] Philadelphia Dept Vet Affairs Med Ctr, Philadelphia, PA USA
[3] Univ Penn, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[4] Univ Calif San Francisco, Dept Dermatol, San Francisco, CA 94143 USA