1. Department of Dermatology, Venereology and Allergology; Ruhr University Bochum; 44791 Bochum Germany
2. Information Network of Departments of Dermatology (IVDK); Georg August University Göttingen; 37075 Göttingen Germany
3. Department of Dermatology and Venereology; Martin Luther University Halle-Wittenberg; 06120 Halle (Saale) Germany
4. Department of Dermatology and Allergology; Philipps University Marburg; 35043 Marburg Germany
5. Institute for Biometrics and Epidemiology, German Diabetes Center (DDZ); 40225 Düsseldorf Germany