BACKGROUND
Linezolid, a synthetic oxazolidinone-class antibiotic, has become an essential reserve treatment for various antimicrobial-resistant infections, including methicillin-resistant Staphylococcus aureus pneumonia and vancomycin-resistant enterococcal bacteremia. Less commonly, linezolid is used to treat highly resistant strains of tuberculosis. A rare side effect of linezolid is black hairy tongue (BHT), in which elongated papillae on the dorsal tongue produce a characteristic blackened appearance. Although benign and self-limiting, the condition can have psychosocial implications due to its hygiene-related stigma. We describe a case of BHT during linezolid treatment for intestinal tuberculosis, then discuss its implications and management.
CASE REPORT
A 33-year-old man receiving treatment for intestinal tuberculosis presented to the clinic with black discoloration of the tongue. Two weeks earlier, his antibiotic regimen had been changed to isoniazid, ethambutol, moxifloxacin, and linezolid due to abnormal liver function test results. He reported no pain, changes in taste, or discomfort; he denied smoking, alcohol use, and coffee or tea consumption. A review of systems was negative, his vital signs were normal, and no laboratory abnormalities were noted. After discontinuation of linezolid and encouragement of good oral hygiene, the discoloration rapidly improved and completely resolved within 3 weeks. The Naranjo algorithm (used to assess causality) indicated that linezolid was the probable causative medication.
CONCLUSIONS
Although rare, linezolid-induced BHT should be considered in patients presenting with acute tongue discoloration. Withdrawal of the offending medication usually resolves BHT but may disrupt management of the underlying condition. During BHT management, physicians should consider both patient preferences and the clinical context of each case.

Keywords: Drug-Related Side Effects and Adverse Reactions; Linezolid; Tongue, Hairy; Tuberculosis