1. Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia2Department of Dermatology, University of Pennsylvania Perelman School of Medicine, Philadelphia
2. Department of Dermatology, University of Pennsylvania Perelman School of Medicine, Philadelphia
3. Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia
4. Valeant Pharmaceuticals International, Bridgewater, New Jersey