Dermatologic toxicity from immune checkpoint blockade therapy with an interstitial granulomatous pattern

Immunotherapies targeting cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death 1 (PD-1) receptor and its ligand (PD-L1) have showed significant therapeutic benefit in patients with clinically advanced solid malignancies, including melanoma. However, immune-related adverse events (irAE) are common, and novel dermatologic toxicities continue to emerge as more patients are treated with immunotherapy. Here we describe a patient treated with combination immunotherapy of ipilimumab and pembrolizumab, who developed asymptomatic erythematous patches on both legs. Histopathologic examination revealed a cutaneous interstitial granulomatous dermatitis. Notably, our patient did not require cessation of immunotherapy for these lesions, which subsequently remained stable, while the patient's melanoma remained controlled. This case expands the dermatologic toxicity profile of immune checkpoint blockade, as recognition of such toxicities is critical to optimal patient management.