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.