black hairy tongue ( bht ) is a self limiting benign condition , characterized by elongation and hypertrophy of filiform papillae of tongue with brown or black discoloration on the posterior dorsum of tongue . increase in keratin production or decrease in normal desquamation may lead to accumulation of keratinized layers . bht is usually asymptomatic , sometimes patients may complain of nausea , halitosis , dysguesia , tickling of the tongue . smoking or chewing tobacco , poor oral hygiene , xerostomia , substance abuse like cocaine , using peroxide containing mouth washes and drugs like steroids , bismuth , methyldopa , tetracycline are the predisposing factors . interestingly , olanzapine along with lithium produced recurrent black hairy tongue in bipolar disorder patient . the incidence of black hairy tongue in patients receiving linezolid was 0.2% in a large controlled study done by hau.t . there is no case report of black hairy tongue in south indians due to linezolid therapy found through pubmed search . here we report a rare case of linezolid induced black hairy tongue in a 10-year - old boy . a 10-year - old boy was referred from orthopaedic department for the complaint of black discoloration of dorsum of tongue for 4 days duration . he was treated with tablet linezolid 600 mg twice daily for two weeks for post surgical infection of left side radial neck fracture . the boy reported the blackish pigmentation of the posterior aspect of dorsum of tongue on the fourteenth day of tablet linezolid . on examination of the oral cavity , black to brown discoloration was seen in the posterior aspect of dorsal surface of tongue , with elongated and hypertrophied filiform papillae [ figure 1 ] . patient was followed after 7 days and the discoloration of tongue totally disappeared [ figure 2 ] . total disappearance of lesion in 11 days after stopping linezolid ] . employing the naranjo adr probability scale to find out the association of linezolid intake to black hairy tongue , the score was five , which revealed a probable adverse drug reaction . the clinical findings and naranjo probability scale had suggested the diagnosis of black hairy tongue due to linezolid therapy . black hairy tongue in a ten year old boy on linezolid photo after stopping linezolid therapy using the naranjo 's adverse drug reaction probability scale , we present a case of probable linezolid - induced bht in a 10-year - old boy . linezolid is an oxazolidinone derivative mainly indicated for infections caused by methicillin - resistant staphylococci and vancomycin - resistant enterococci . reversible bone marrow suppression and neuropathy would occur , if the duration of the drug intake is more than 4 weeks . the median time duration of development of black hairy tongue after starting linezolid in previous case reports were two weeks . , described the association of linezolid with both black hairy tongue and discoloration of teeth in three children . defective desquamation of keratinized layer of tongue leads to excessive growth and thickening of filiform papillae of tongue which leads to collection of microorganisms or foreign material . the diagnosis of drug induced black hairy tongue depends upon the visual inspection of the discolored , elongated and hypertrophied filiform papillae . detailed history of the patient helps us to identify the offending drug and the associated contributing factors . treatment of the black hairy tongue is immediate withdrawal of the offending drug and proper tongue debridement . in persistent type , it could be treated with 40% urea , salicylic acid and surgical excision . this case is presented for its rarity in occurrence induced by linezolid in a 10-year - old boy and to create awareness among physicians about this rare side effect . the patient on linezolid therapy should be advised to maintain a good oral hygiene to prevent the development of bht . further investigations are needed to find out the pathogenesis for linezolid induced black hairy tongue .
black hairy tongue ( bht ) also called as lingua villosa nigra , is a self limiting benign condition characterized by hypertrophy and elongation of filiform papillae of tongue with brown or black discoloration . 
 smoking , poor oral hygiene , xerostomia , using peroxide containing mouth washes , substance abuse and drugs ( steroids , methyldopa , olanzapine , etc ) are the predisposing factors . 
 however its occurrence in relation to linezolid ingestion among south indians has not been reported in pubmed database . here 
 we report a case , where significant association of linezolid intake with bht was found in a 10-year - old boy , who was treated with tablet linezolid for post surgical infection of left side radial neck fracture . 
 this case is reported for the rarity of occurrence with linezolid therapy . according to naranjo adverse drug reaction ( adr ) causality scale , 
 the association of bht due to linezolid in our case was probable .