Abstract: A 57-year-old male presented with psoriasiform eruption, palmoplantar pustulosis and severe nail involvement during treatment with pembrolizumab for lung cancer. He had no personal or family history of psoriasis. The histopathological findings were in accordance with psoriasis. The psoriatic lesions subsided after treatment with acitretin combined with NB-UVB. A total of 25 cases of psoriasis induced by immune checkpoint inhibitors (ICIs) have been reported. The majority of the patients were elderly men with lung cancer or melanoma, and the most frequently reported ICIs were nivolumab and pembrolizumab. The median delay between introduction of ICIs and psoriasis occurrence was 9 weeks. The clinical type was mainly plaque psoriasis and the histopathological manifestations were in accordance with classic psoriasis. The lesions were improved in all patients after topical medications, phototherapy, and/or systemic treatments, and ICIs were continued in most cases.

Key words: immune checkpoint inhibitors, PD-1, pembrolizumab, psoriasis, immune-related adverse events