Black Hairy Tongue as a Rare Adverse Effect of Linezolid in Multidrug‐Resistant Tuberculosis: A Case Report

Black hairy tongue (BHT), or lingua villosa nigra, is a rare adverse effect of linezolid, an antibiotic frequently used in the treatment of multidrug‐resistant tuberculosis (MDR‐TB). We present a case of a 24‐year‐old female who developed BHT while receiving linezolid as part of a longer regimen for MDR‐TB. The patient exhibited a typical BHT presentation, with painless brown‐to‐black discoloration on the posterior dorsal surface of her tongue, appearing 25 days after initiating linezolid therapy. There were no other identifiable contributing factors. Upon discontinuation of linezolid and a shift to a modified regimen, the BHT completely resolved within 10 days. A Naranjo Adverse Drug Reaction Probability Scale score of 5 suggested a probable causal relationship between linezolid and BHT. This report represents the first documented case of linezolid‐associated BHT from Nepal, highlighting the importance of clinicians' awareness of this rare but clinically significant side effect, especially within the context of MDR‐TB treatment, to provide prompt diagnosis, reassurance, and appropriate management.