Abstract

The advent of immune checkpoint inhibitors (ICIs), specifically anti-PD-1/PD-L1 antibodies,  for a wide variety of advanced solid tumors has heralded a new spectrum of cutaneous immune adverse events (iAEs). Psoriasiform drug eruption is a dermatologic toxicity that has been documented in the setting of ICI therapy. Although these cases have been documented in the literature, most reports neglect to provide a detailed description of the histopathological findings associated with the psoriasiform eruption. Herein, we report three original cases of psoriasiform drug eruption in patients receiving anti-PD-1/PD-L1 inhibitors with comprehensive histopathologic analysis. The mean time to onset of psoriasiform toxicity was 24 days (range: 1-45 days) from initiation of ICI therapy. Lesions most frequently presented on the extremities and trunk as plaques and papules. Of the three skin biopsies examined, all demonstrated psoriasiform hyperplasia, superficial perivascular lymphocytic infiltrate, epidermal neutrophilic parakeratosis, dermal eosinophils and scattered dyskeratosis. Additional histologic features observed in these biopsies included hypogranulosis, spongiosis, adnexal involvement, and dermal plasma cells. One biopsy showed the additional specific findings of an interface dermatitis component and intracorneal neutrophils. ICI treatment was discontinued in all of these cases, and all skin lesions ultimately resolved. One case was treated solely with topical corticosteroids, and the other two were additionally given systemic medications including oral steroids, interleukin-23 inhibitors, and TNF-alpha inhibitors. Further study of the signaling pathways, antibody-mediated mechanisms, and activated T cell populations in psoriasiform pattern anti-PD-1/PD-L1 cutaneous manifestations may provide greater insight to the specific histologic findings observed in this cohort.