Division of Dermatology, Departments of Medicine and Pediatrics, School of Medicine, Washington University School of Medicine, St. Louis, MO, USA. Philadelphia College of Osteopathic Medicine, Philadelphia, PA, USA. Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. Section of Dermatology, Children's Hospital of Philadelphia, Philadelphia, PA, USA.