Rapid progression to toxic epidermal necrolysis following switch of PD-1 inhibitors: a case report.

Immune checkpoint inhibitors (ICIs) have been widely used in clinical practice in recent years. Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare, potentially life-threatening cutaneous adverse reactions associated with ICIs. This report describes a 69-years-old male with recurrent hypopharyngeal cancer who experienced only recurrent Grade 1 maculopapular rash during treatment with tislelizumab combined with chemotherapy and subsequent maintenance therapy. However, within 2 days after switching to pembrolizumab, his condition deteriorated rapidly into TEN, involving over 95% of the body surface area and multiple mucosal sites including the oral cavity and conjunctivae. Skin biopsy revealed epidermal necrosis, subepidermal clefts, and infiltration of CD4 and CD8 positive T lymphocytes. Immunohistochemistry demonstrated positive PD-L1 expression but negative PD-1 expression. These pathological findings suggested that alterations in the local cutaneous immune microenvironment following sequential administration of different PD-1 inhibitors might play a critical role in the fulminant progression of TEN.