Drug-Induced SCLE — SCE Dermatology MCQ

Correct answer: B — Terbinafine

The correct answer is B, Terbinafine. Terbinafine is the antifungal most consistently and repeatedly reported as the leading cause of drug-induced subacute cutaneous lupus erythematosus (SCLE), producing photodistributed annular polycyclic plaques on the trunk and arms that are clinically indistinguishable from idiopathic SCLE. The emc SmPC for terbinafine specifically warns that it should be used with caution in patients with pre-existing lupus erythematosus because of post-marketing reports of occurrence or deterioration of cutaneous or systemic lupus. Anti-Ro (SSA) positivity, as in this patient, is a recognised serological feature of both idiopathic and drug-induced SCLE, and the eruption typically resolves after withdrawal of the offending drug, supporting terbinafine as the culprit here. Why the other options are wrong: D. Ciclosporin: This is an immunosuppressant used to treat lupus and other autoimmune skin disease, it is not a recognised trigger of drug-induced SCLE. C. Amoxicillin: Amoxicillin is associated with morbilliform drug eruptions and, rarely, DRESS, but it is not among the classically implicated agents for SCLE. A. Methotrexate: Methotrexate is used as a steroid-sparing treatment for cutaneous and systemic lupus, not as a cause of drug-induced lupus. E. Paracetamol: Paracetamol is not linked to drug-induced lupus syndromes; hepatotoxicity, not autoimmune skin eruption, is its principal adverse effect of concern. Key point: Terbinafine is the antifungal most strongly and consistently linked to drug-induced SCLE, and prescribers should be cautious in patients with a lupus history or photosensitivity.

Reference: electronic medicines compendium (emc), Terbinafine 250mg Tablet SmPC, Special warnings and precautions for use: caution in patients with pre-existing psoriasis or lupus erythematosus due to post-marketing reports of cutaneous/systemic lupus erythematosus, https://www.medicines.org.uk/emc/product/7133/smpc