Multiple Eruptive Keratoacanthomas Secondary to Nivolumab Immunotherapy.

Immune checkpoint inhibitors are increasingly being utilized for the treatment of advanced neoplastic disease and have been associated with wide-ranging cutaneous adverse effects. Though exceedingly rare, eruptive keratoacanthomas have been associated with the use of immune checkpoint inhibitors such as pembrolizumab and nivolumab, whose molecular target is the programmed cell death protein 1. Herein, we detail a case of numerous eruptive keratoacanthomas arising in a patient one month after initiation of nivolumab for recurrent metastatic oropharyngeal squamous cell carcinoma. Treatment with multiple rounds of intralesional corticosteroids and a several-month course of oral acitretin resulted in partial improvement. Subsequent treatment with intralesional 5-fluorouracil demonstrated near-complete resolution of the keratoacanthomas without discontinuation of nivolumab. Although eruptive keratoacanthomas secondary to immune checkpoint inhibitors are exceptionally rare, physicians should be aware of this cutaneous adverse effect as their use becomes more widespread.