Severe Oral Mucositis: A Rare Adverse Event of Pembrolizumab.

Treatment of malignancy with anti-programmed cell death 1 (PD-1) immune checkpoint inhibitors can cause mucocutaneous side effects resulting from T cell activation. Due to their recent development, the full side effect profile remains to be fully elucidated, however dermatologic adverse events are most common. The main oral toxicities of these immune checkpoint inhibitors include: xerostomia, dysgeusia, and lichenoid reactions. Oral mucositis occurs more rarely in the setting of PD-1 inhibition, and few other reports of a Grade 3 or higher, severe, stomatitis have been reported in the literature. We present a case of a 78-year-old woman with Grade 3 ulcerative oral mucositis that occurred 13 months after initiation of PD-1 inhibitor, pembrolizumab, for the treatment for lung adenocarcinoma. She was successfully treated with prednisone, and pembrolizumab was temporarily held by her oncologist. Physicians should be aware of the possibility of severe mucositis in the setting of PD-1 inhibitors, as well as the management. J Drugs Dermatol. 2018;17(7):807-809.