Antitubercular drug-induced lichen planus: A case study with a mini literature review.

Introduction: Drug-induced lichen planus is a cutaneous adverse effect that manifests as a systemic eruption of flat-topped, erythematous, or violaceous papules resembling lichen planus on the trunk and extremities. Although antitubercular therapy has been linked to cutaneous hypersensitivity reactions, the literature on such cases is scarce. Here, we present a case to contribute to this field, reporting on its presentation and management, and reviewing previous case studies. Case Report: Our patient, a 63-year-old male, presented with black pigmented patches on the skin, having been diagnosed with pulmonary tuberculosis and on antitubercular therapy for the past two months. A diagnosis of ATT-induced lichen planus was made, and all ATT was stopped. The patient was treated with antihistamines, apremilast, tacrolimus, and corticosteroids, and rechallenge of each drug was performed consecutively. No new lesions appeared after rechallenge with isoniazid and rifampicin. However, ethambutol was not reintroduced due to strong suspicion, by exclusion, that it was the offending agent, whereas on rechallenge with isoniazid and rifampicin, the patient's skin lesions gradually improved with eventual resolution of hyperpigmentation. Discussion and Conclusion: Lichenoid drug eruptions are characterized by type IV hypersensitivity reactions, and rechallenge is required to ensure safer treatment since the risk of disseminated and multi-drug-resistant tuberculosis increases with the cessation of antitubercular therapy.