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.

Introduction

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.[1] Increase in keratin production or decrease in normal desquamation may lead to accumulation of keratinized layers.[2] BHT is usually asymptomatic, sometimes patients may complain of nausea, halitosis, dysguesia, tickling of the tongue.[1] 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.[3] Interestingly, olanzapine along with lithium produced recurrent black hairy tongue in bipolar disorder patient.[4] The incidence of black hairy tongue in patients receiving linezolid was 0.2% in a large controlled study done by Hau.T.[5] 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.

Case Report

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]. Complete hemogram was normal. Parents did not give consent for biopsy of the lesion. Linezolid was stopped after the tongue discoloration. Patient was asked to clean his tongue with normal saline twice daily. 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.

Figure 1

Black hairy tongue in a ten year old boy on linezolid

Figure 2

Photo after stopping linezolid therapy

Discussion

Using the Naranjo's Adverse Drug Reaction Probability Scale, we present a case of probable linezolid-induced BHT in a 10-year-old boy. The patient was not on any other medications except linezolid. Other known causes of BHT were ruled out.

Linezolid is an oxazolidinone derivative mainly indicated for infections caused by methicillin-resistant staphylococci and vancomycin-resistant enterococci. The most common side effects of linezolid are nausea, vomiting and headache. 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.[6] Petropoulau T et al., described the association of linezolid with both black hairy tongue and discoloration of teeth in three children.[7]

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 exact mechanism behind drug induced BHT is not known.[6] 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.[8] 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.

Conclusion

Linezolid induced BHT is a rare and benign disorder. Other predisposing factors should be excluded before diagnosing linezolid induced BHT. 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.