1. Dermatology Department Leiden University Medical Center Leiden the Netherlands
2. Université de Paris, Institut de Recherche Saint‐Louis, INSERM UMR1160 Paris France
3. Haematology Laboratory
4. Departement of Dermatology AP‐HP, Hôpital Saint‐Louis Paris France
5. Université de Paris, Institut de Recherche Saint‐Louis, INSERM UMRS976 Onco‐Dermatology and Therapies Paris France
6. Dermatological Clinic, Department of Medical Sciences University of Turin Medical School Turin Italy
7. St. John’s Institute of Dermatology, School of Basic and Medical Biosciences King’s College London, Guy’s Hospital London SE1 9RT UK