Eosinophilic folliculitis of the scalp associated with PD-1/PDL1 inhibitors

Background: Immune checkpoint inhibitors are monoclonal antibodies which target immune “checkpoints” enhancing T cell–mediated cytotoxic and antitumor responses. Together to the amazing results, these drugs are associated with some peculiar adverse events called immune-related adverse events. Alopecia is one of these. It is usually reported to be clinically and histologically similar to alopecia areata. Aims: We report a case of eosinophilic folliculitis of the scalp occurred during nivolumab therapy, its management and some pathogenetic hypotheses. Patient: Herein, we report the first case of eosinophilic folliculitis of the scalp occurred during nivolumab therapy, firstly appeared as a lichen planopilaris. Topical steroids and fusidic acid cream were applied with partial benefit and a scaring outcome. No discontinuation of nivolumab was required. Conclusion: Immune checkpoint inhibitors induced inflammatory response leads to the exposure of hair follicle antigens and a consequent loss of Immuno Privilege. We hypothesize a role of steroids in deviating a primarily lichenoid reaction toward a folliculitis.