1. Program for Clinical Research; Department of Dermatology; University of California; San Francisco School of Medicine; San Francisco CA U.S.A.
2. Faculty of Medicine; University of Ottawa; Ottawa Ontario Canada
3. University of California, Los Angeles; David Geffen School of Medicine at UCLA; Los Angeles CA U.S.A.
4. Department of Dermatology; University of Pennsylvania Perelman School of Medicine; Philadelphia PA U.S.A.
5. Department of Dermatology; Vanderbilt University Medical Center; Nashville TN 37204 U.S.A.
6. Unit for Population-Based Dermatology Research; St John's Institute of Dermatology; Guy's & St Thomas' NHS Foundation Trust and King's College London; Chicago IL U.S.A.
7. Departments of Dermatology, Preventive Medicine and Medical Social Sciences; Northwestern University Feinberg School of Medicine; Chicago IL U.S.A.
8. Department of Biostatistics, Epidemiology and Informatics; University of Pennsylvania Perelman School of Medicine; Philadelphia PA U.S.A.
9. Faculty of Epidemiology and Population Health; London School of Hygiene and Tropical Medicine; London U.K.