Abemaciclib-induced Lichenoid Dermatitis: A Rare Case Report

Abemaciclib is an oral cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) that plays a key role in treating hormone-sensitive HER2-negative metastatic breast cancer. Abemaciclib, due to its higher selectivity for CDK4 tends to cause fewer hematologic issues, but more gastrointestinal problems, particularly diarrhea, and fatigue, leading to poor tolerability. Dermatologic side effects specifically associated with abemaciclib are less frequently reported. We are reporting a rare instance of lichenoid dermatitis caused by abemaciclib in a 54-year-old female diagnosed with breast cancer after 9 months of intake of the drug. She developed multiple pruritic papules and erythematous, hyperpigmented, ill-defined plaques with mild scaling over the surface present over the bilateral leg and hand, with histology suggestive of drug-induced lichenoid dermatitis. Along with discontinuing abemaciclib, she was treated with oral prednisolone, topical clobetasol propionate 0.05% cream, oral antihistamines, and emollient. This case report highlights lichenoid dermatitis induced by abemaciclib, contributing valuable insight to the limited literature on CDK4/6 inhibitor-related lichenoid reactions.