1. Policlinic for Dermatology and Venereology, Saint Kliment Ohridski University, Medical Faculty, University Hospital Lozenetz, Sofia, Bulgaria
2. Department of General and Clinical Pathology, Medical Faculty, “Saint Kliment Ohridski University” Sofia, Bulgaria
3. Department of General and Clinical Pathology, Medical Faculty, Trakia University, Stara Zagora, Bulgaria
4. Onkoderma- Policlinic for Dermatology and Dermatologic Surgery, General Skobelev 26 Sofia, Bulgaria
5. Department of Medicine and Science of Aging “G. D'Annunzio” University, Chieti, Italy
6. Department of Dermatology and Allergology, Hospital Dresden-Friedrichstadt, Academic Teaching Hospital of the Technical University of Dresden, Dresden, Germany