Abstract

Cutaneous toxicities are one of the most prevalent adverse effects associated with immune checkpoint inhibitors (ICIs) affecting up to 30-60% of patients. We review a case of lichenoid tissue reaction of the vulva following pembrolizumab. A 78-year-old woman with metastatic endometrial carcinoma presented with a 5-month history of vulvar burning. She had started pembrolizumab ten months prior. Physical exam was notable for bright red plaques around the vaginal introitus. Remainder of the skin including oral exam was unremarkable. Vulvar biopsy from the right vestibule showed a dense lichenoid band at the dermal epidermal junction with many dyskeratotic epidermal keratinocytes and focal subepidermal clefting and suprabasal acantholysis. Direct and indirect immunofluorescence and ELISA for desmogleins and BP 180/230 were negative. She was initiated on clobetasol ointment. Lichenoid drug reactions are a well reported and delayed cutaneous side effect in those receiving ICIs. By removing inhibition of CTLA-4 and PD-1 on self-reactive T cells, autoimmune disease may arise or worsen on ICIs. Inflammatory vulvar dermatoses associated with ICIs, however, are rarely reported in the literature. There are scattered reports of lichen sclerosus associated with ICIs. Lichenoid drug reactions of the vulva resembling erosive lichen planus have not previously been reported with ICIs to our knowledge. Erosive vulvar lichen planus is generally considered challenging to treat. Furthermore, research indicates that other ICI-associated lichenoid vulvar eruptions such as lichen sclerosus are refractory to first-line topical corticosteroids in 76% of patients. Prompt diagnosis and treatment will improve outcomes for these patients.