A Rare Dual Complication of First-Line Anti-tubercular Therapy: A Case Report of Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS) Syndrome and Ethambutol-Induced Optic Neuropathy.

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is an extremely rare and serious systemic drug reaction, often posing significant diagnostic challenge to clinicians. Ethambutol-induced optic neuropathy (EON) is a well-recognised but often insidious complication of first-line anti-tubercular therapy (ATT), typically manifesting as reduced visual acuity, and visual field defects. We report the case of a 78-year-old woman with confirmed diagnosis of pulmonary tuberculosis, who simultaneously developed probable DRESS syndrome, secondary to rifampicin and EON shortly after initiation of the standard first-line ATT regimen (isoniazid, rifampicin, pyrazinamide, and ethambutol). Early diagnosis and prompt withdrawal of the offending drugs helped her to achieve complete recovery with no complications. This case highlights the importance of a high index of suspicion and early recognition of drug-induced adverse reactions in patients on multi-drug ATT regimens, as timely diagnosis and management can help in preventing serious complications like permanent vision loss, and also death.