Rapid-onset black hairy tongue following clomipramine initiation and rechallenge: A case report

Black hairy tongue (BHT), a benign condition characterized by hypertrophy of the filiform papillae and discoloration of the dorsal tongue, is commonly associated with antibiotic use, poor oral hygiene, lifestyle factors, and general health issues. By contrast, psychotropic drug-induced BHT is rare and typically emerges weeks to months after treatment initiation. We report the case of a 42-year-old male patient with recurrent major depressive disorder and prior use of different psychotropic medications who developed BHT within days of initiating clomipramine on two separate occasions. In the first trial, BHT resolved shortly after clomipramine discontinuation. On the second occasion, considering the effectiveness of the treatment, the absence of concerning symptoms, and the exclusion of other causes through multidisciplinary evaluation, the patient remained on clomipramine. Despite oral hygiene measures, BHT persisted. Close temporal association, reproducibility upon re-challenge, resolution upon discontinuation during the first trial, and absence of alternative explanations supported a definite causal link, as indicated by the Expanded Naranjo Adverse Drug Reaction Probability Scale. Chronic smoking and prolonged chlorhexidine mouthwash use may have contributed, though these were unlikely the individual causes. To our knowledge, this is the first report of clomipramine-induced BHT with such rapid onset and recurrence. This case highlights the importance of recognizing BHT as a potential early-onset side effect of tricyclic antidepressants, particularly clomipramine. Prompt recognition, interdisciplinary assessment, and consideration of the risk-benefit balance are essential. Although an idiosyncratic reaction – independent of clomipramine-induced xerostomia – can be hypothesized, further research is needed to clarify the mechanisms underlying antidepressant-induced BHT.