Lichenoid Drug Eruption From Cetirizine Treated With Upadacitinib and Dupilumab.

Cutaneous lichenoid drug eruptions (LDE) are a group of relatively uncommon adverse drug reactions characterized by widespread erythematous to violaceous scaly papules that can be difficult to differentiate from idiopathic lichen planus. Their increasing prevalence with the use of biologics, tyrosine kinase inhibitors, and immune checkpoint inhibitors has become of particular interest in dermatology. More commonly used medications, including antibiotics, antihypertensives, and nonsteroidal anti-inflammatory drugs, have also been reported to cause LDEs. While the exact pathophysiology of LDE remains to be fully elucidated, certain medications are believed to increase the antigenicity of skin proteins, thereby triggering a T-cell-mediated response via CD8+ cytotoxic T lymphocytes that target basal keratinocytes, while increased interferon γ signaling further amplifies the inflammatory process. Herein, we report a case of LDE induced by an antihistamine (cetirizine) successfully treated with both upadacitinib and dupilumab after failure of systemic corticosteroids.