Black hairy tongue: an early adverse effect of linezolid in treatment of multidrug resistant tuberculosis.

A man in his 20s with microbiologically confirmed multidrug-resistant pulmonary tuberculosis was initiated on a regimen comprising bedaquiline, pretomanid, linezolid and moxifloxacin. Within 2-3 weeks, he developed altered taste sensation followed by black discolouration of the tongue. In accordance with clinical examination and temporal association linezolid was considered the likely causative agent and was discontinued, while the remaining regimen was continued. The patient was advised on oral hygiene measures with which complete resolution occurred within 8-10 days, with no recurrence on follow-up and he was transitioned to an individualised longer regimen.This case highlights that black hairy tongue is a rare, early and reversible adverse effect of linezolid. Prompt recognition and appropriate management can prevent unnecessary discontinuation of effective multidrug-resistant tuberculosis therapy and improve treatment adherence.