1. Department of Dermatology, University of Pennsylvania Perelman School of Medicine, Philadelphia
2. Section of Pediatric Dermatology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
3. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia
4. Department of Biostatistics, Epidemiology and Informatics, University of Pennsylvania Perelman School of Medicine, Philadelphia
5. Department of Allied Health Sciences, School of Medicine, University of North Carolina-Chapel Hill, Chapel Hill