1 Department of Dermatology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, U.S.A.
2 Division of Nephrology, The Children's Hospital of Philadelphia, Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, U.S.A.
3 Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, U.S.A.