PD-1 inhibitor-associated lichenoid inflammation with incidental suprabasilar acantholysis or vesiculation-Report of 4 cases.

BACKGROUND: Immune checkpoint agents targeting programmed cell death-1 protein (PD1) or cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) receptors are increasingly utilized in treatment of advanced malignancies. However, these immunotherapies are commonly associated with idiosyncratic cutaneous adverse reactions. Thus, recognition and awareness of these reactions are necessary.

METHODS: We reviewed the skin biopsies of all patients on anti-PD1 therapy with or without ipilimumab who developed lichenoid inflammation and included those with microscopic suprabasal or intraepidermal clefts.

RESULTS: Four patients presented with interface dermatitis with microscopic intraepidermal clefts. In 2 patients, the clefts were well developed and had some acantholytic cells while the other 2 appeared to be spongiosis or inflammation related. Immunofluorescence was negative in 1 patient. None of them had clinical findings in keeping with paraneoplastic pemphigus (PP) and the symptoms improved with either topical corticosteroid or withdrawal of immunotherapy.

CONCLUSIONS: Lichenoid drug reaction occurring in patients receiving anti-PD1 therapy may be associated with microscopic suprabasal or intraepidermal clefting. The clinical course was similar to lichenoid drug reactions without clefting even though some lesions may resemble PP microscopically.