Ethambutol induced subacute cutaneous lupus erythematosus in an elderly female with co-morbidities

Papulosquamous lesions in an elderly female with multiple co-morbidities often pose diagnostic challenge. We present an interesting case of anti-tubercular treatment (ATT) induced sub-acute cutaneous lupus erythematosus. The patient presented with papulosquamous lesions in generalised distribution, which showed interface dermatitis on histopathology. The serology for anti-nuclear antibodies, anti-Ro and anti-La was positive. The rash resolved spontaneously after stopping all the suspected drugs. Oral provocation was performed with first line anti-tubercular drugs and ethambutol was found to be the culprit drug, which was later confirmed by reappearance of skin rash by inadvertent ingestion of one dose of ethambutol by the patient.