J Chéret1,2, J Gherardini1, M Bertolini1, R Paus2,3. 1. Monasterium Laboratory, Münster, Germany. 2. Dr Phillip Frost Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, U.S.A. 3. Centre for Dermatology Research, University of Manchester, and NIHR Manchester Biomedical Research Centre, Manchester, U.K.