Affiliation: | 1. Department of Dermatology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania;2. Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania;3. Department of Dermatology, University of Utah School of Medicine, Salt Lake City, Utah;4. National Psoriasis Foundation, Portland, Oregon |