Ethambutol-induced Oral Lichenoid Drug Eruption: An Uncommon Occurrence

Dear Editor, Skin eruptions caused by certain drugs and compounds can be similar to lichen planus (LP). The term lichenoid (LP-like) describes these reactions. A long list of drugs can produce a lichenoid drug eruption (LDE), which is increasing steadily. Oral lichenoid lesions (OLLs) and oral lichenoid drug eruptions (OLDEs) are clinically and histologically identical to classical oral lichen planus (OLP). Detailed treatment history, especially medications taken and distinct clinical appearance with subsequent resolution following drug cessation, are essential in an accurate diagnosis of OLDE.[1] Cutaneous LDEs are known as adverse effects of ethambutol, but OLDE is uncommon. Here, we report a case of OLDE in a tuberculosis (TB) patient caused by ethambutol. A 64-year-old female presented to the dermatology department of our hospital with the chief complaint of violaceous eruption on bilateral buccal mucosa and erosion on the lower lip for a week. The above lesions were associated with pain and burning, especially when taking hot and spicy food. On examination, ill-defined violaceous plaques over bilateral buccal mucosa and erosive plaque over the lower lip were seen [Figure 1]. Skin, hair, nails, and other mucosal examinations were within normal limits. The patient was on antitubercular treatment (Directly observed therapy short course [DOTS]) for right tubercular pleural effusion for 2 months. There is no history of diabetes, hypertension, or any other chronic illness in the patient.Figure 1: Ill-defined violaceous plaques over buccal mucosa (a) and erosive plaque over lower lip (b)There was no history of any smoking or substance abuse. There was no similar complaint in the family. There was no history of any dental procedures. A biopsy was advised for histopathologic evaluation, but the patient refused for the same. A dental reference was asked to rule out other causes of OLDE. The patient was put on tacrolimus 0.1% in an Orabase gel for local application twice daily. Ethambutol was stopped, and the patient was shifted to an alternate antitubercular regimen, following which lesions started subsiding within a few days. Based on the above findings, a diagnosis of Oral LDE due to ethambutol was made. Ethambutol is one of the first lines of treatment for TB, along with rifampicin, isoniazid, and pyrazinamide. It is considered a bacteriostatic drug, interfering with the biosynthesis of arabinogalactan in the cell wall, halting multiplying bacilli. Although cutaneous LDE is a known adverse event to ethambutol, oral LDE is uncommon.[2] Clinical diagnostic criteria for OLP and OLLs:[3,4] Bilateral presentation, more or less symmetrical lesions Presence of white striae (reticular pattern) Erosive, atrophic, bullous, or plaque manifestations are only accepted as subtypes when always accompanied by reticular lesions located anywhere in the mucosa. The term “clinically compatible with” is to be used with all lesions similar to OLP that do not meet the mentioned criteria Classification of OLLs:[5] Amalgam restoration, topographically associated OLL Drug-related OLL OLL in chronic graft versus host disease OLL, unclassified (e.g., erythematous changes limited to the gingiva without signs of “classic” OLP elsewhere in the oral cavity, or lesions that have a LP like aspect but that lack one or more characteristic clinical features, such as a bilateral presentation). Although OLDEs are not life-threatening conditions, a thorough history regarding the patient’s past medical history, including also personal and family history of allergies, as well as an accurate and complete drug history, including not only the suspect offending medication(s) but also the concurrent one(s), whether they are prescribed, or over-the-counter, or alternative remedies, might help in reducing the chance of developing OLDEs.[6] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.