Atezolizumab-Induced Generalized Cutaneous Lichen Planus in a Patient With Metastatic Small Cell Lung Cancer Successfully Treated With Isotretinoin: A Case Report.

Immune checkpoint inhibitors, now widely used in treating various malignancies, increase the risk of autoimmune reactions and immune-related adverse events (irAEs), with skin toxicities being the most frequent. These agents enhance the immune response against tumors by blocking the suppression of cytotoxic T lymphocytes. Here, we report a rare case of generalized cutaneous lichen planus induced by atezolizumab, an immune checkpoint inhibitor administered for small cell lung cancer. After consulting with the oncologist, we opted to initiate isotretinoin as the first-line treatment. Considering the patient's oncologic status and multiple comorbidities, we aimed to avoid systemic corticosteroids due to their potential side effects. This case was effectively managed with low-dose oral isotretinoin alongside high-potency topical corticosteroids. It emphasizes the need to consider retinoids as a potential treatment option for various dermatological conditions beyond acne. Isotretinoin may be beneficial in treating lichen planus by influencing cellular proliferation and promoting epithelial differentiation, though its exact mechanism remains uncertain. Additionally, it has notable anti-inflammatory effects and modulates immune responses. In such cases, isotretinoin may also enhance the therapeutic effects of topical corticosteroids through a synergistic interaction.