Ethambutol-Induced Severe Cutaneous Hypersensitivity: A Case of Recurrent Smear-Negative Pulmonary Tuberculosis in a Poorly Controlled Diabetic Patient

Abstract

Diabetes mellitus is a well-established risk factor for tuberculosis (TB), influencing disease severity, recurrence, and treatment outcomes. We report a case of recurrent smear-negative pulmonary tuberculosis in a 63-year-old patient with poorly controlled type 2 diabetes mellitus who had completed anti-tubercular therapy five years earlier. Upon re-initiation of standard first-line therapy, the patient developed a severe generalized cutaneous hypersensitivity reaction during the intensive phase. Sequential drug re-challenge identified ethambutol as the causative agent. Withdrawal of ethambutol led to complete resolution of dermatological manifestations, and the treatment regimen was modified accordingly. This case highlights the bidirectional relationship between diabetes and TB, diagnostic challenges of smear-negative disease, and the importance of systematic drug evaluation in anti-tubercular therapy-related adverse reactions.