Florian Anzengruber,1,2 Adhideb Ghosh,1–3 Julia-Tatjana Maul,1,2 Mathias Drach,1,2 Alexander A Navarini1–3 1Department of Dermatology, University Hospital Zurich, Zurich, Switzerland; 2Faculty of Medicine, University of Zurich, Zurich, Switzerland; 3Competence Center Personalized Medicine University of Zurich/Swiss Federal Institute of Technology (ETH) Zurich, Switzerland Purpose: Several studies have suggested that an HLA-Cw6+ allele can predict an improved outcome of treatment in psoriasis patients. The aim of the study was to assess whether the published association between HLA-Cw6 allele carriers and response to ustekinumab has the potential to impact treatment decisions. Patients and methods: Differences in Psoriasis Activity and Severity Index 50, 75, and 90; Nail Psoriasis Severity Index; and Dermatology Life Quality Index at 16 weeks were evaluated between HLA-Cw6 allele carriers vs. non-carriers. Thirty patients with moderate-to-severe psoriasis under treatment with ustekinumab were included in our study. Results: There was no difference between the two groups with respect to Psoriasis Activity and Severity Index 50, 75, and 90 or in terms of change in Nail Psoriasis Severity Index or Dermatology Life Quality Index. Conclusion: In our retrospectively analyzed cohort, we could not detect the previously reported better response in HLA-Cw6+ vs. HLA-Cw6− patients. Keywords: human leukocyte antigen, Cw6, genetic variations, HLA-Cw6, ustekinumab