Anti-tumor Necrosis Factor-Alpha (TNF-α)-Induced Hypertrophic Lichen Planus: A Case Report.

We report the case of a 26-year-old male patient with a six-year history of inflammatory bowel disease who developed pruritic, hyperpigmented, and hyperkeratotic nodules on his left abdomen three months after switching from adalimumab to infliximab therapy. Clinical examination and histopathological analysis confirmed the diagnosis of hypertrophic lichen planus (HLP), a rare variant of lichen planus characterized by thick, scaly plaques and intense pruritus. Notably, this adverse reaction represents only the second documented instance of anti-tumor necrosis factor-alpha (TNF-α)-induced HLP, highlighting the potential paradoxical cutaneous reactions associated with these therapies. Although the patient's inflammatory bowel disease was well controlled with infliximab, the skin lesions responded only minimally to topical corticosteroids. This case underscores the importance of vigilant monitoring of unusual dermatologic manifestations in patients undergoing anti-TNF-α treatment, particularly because such adverse effects can lead to significant morbidity and may be associated with an increased risk of cutaneous squamous cell carcinoma. The mechanisms underlying this paradoxical reaction remain unclear but may involve a shift in cytokine balance following TNF-α inhibition. Increased clinician awareness and early detection are crucial for managing rare drug-induced eruptions and optimizing therapeutic outcomes.