Case Report: Rapid recurrence of psoriasiform dermatitis upon sequential anti-PD-1 therapy with pembrolizumab and tislelizumab with 3-year follow-up.

Psoriasiform eruption is an uncommon cutaneous immune-related adverse event (irAE) associated with anti-PD-1 therapy, and its rapid recurrence upon switching to a different anti-PD-1 agent is a scarcely documented phenomenon. We report the case of a 59-year-old man with stage IIB lung adenocarcinoma who developed a pruritic, scaly eruption after his fourth cycle of pembrolizumab. Histopathological examination confirmed a diagnosis of grade 2 psoriasiform dermatitis according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The initial episode was resolved with systemic corticosteroids. However, upon switching anti-PD-1 therapy to tislelizumab, a similar but more widespread eruption recurred rapidly within a week. The recurrence was successfully managed with topical corticosteroid and antihistamines, and the anti-PD-1 therapy was subsequently discontinued. During the 3-year follow-up after discontinuation, the patient's skin lesions resolved completely with no recurrence, and no tumor progression was observed. The reduced latency of psoriasiform dermatitis recurrence upon anti-PD-1 inhibitor rechallenge suggests a memory T cell-driven immune response. It also highlights that such irAEs were observed with the two PD-1 inhibitors pembrolizumab and tislelizumab used in this case and can be effectively managed. In this case, tumor progression was not observed after treatment cessation, although causality cannot be inferred.