Ribociclib and palbociclib-induced erythema multiforme: a case report.

Cyclin-dependent kinase 4/6 inhibitors (CKIs), ribociclib, palbocilb and abemaciclib, have been approved in combination with endocrine therapy for the treatment of hormone receptor-positive and human epidermal growth factor 2-negative advanced or metastatic breast cancer. Severe dermatological adverse events are rare with these agents; however, they require direct recognition and management in order not to become life-threatening. Erythema multiforme (EM) belongs to a dermatopathic spectrum that includes immune-mediated, widespread hypersensitivity reaction, which occurs with varying degrees of severity and affects the skin and/or the mucosa. We hereby present a case of ribociclib- and palbociclib-related EM. We sought to report this case given the implication of two agents from the same drug class in EM onset. We also aim to emphasize the breadth of mechanisms of actions of CKIs, with an impingement in the immune system as well, and the importance of promptly identifying and handling such skin toxicities.