Discoloured tongue: a new cause?

Drug-induced black hairy tongue

Black hairy tongue (BHT) is a benign, self-limiting disorder characterized by abnormally hypertrophied and elongated filiform papillae on the surface of the tongue. The prevalence of BHT is quite variable, ranging from 0-53.8% depending on the population. Many predisposing factors to BHT exist, and several drugs and drug classes have been implicated in causing this disorder. A modified Naranjo adverse drug reaction probability nomogram specific for BHT was used to rate causality for the available published case reports of drug-induced BHT. From the available data, antibiotics and drugs capable of inducing xerostomia are the drug classes that have modest evidence of causality and a rational mechanism. The presence of underlying predisposing factors in these cases along with the variable prevalence of BHT make drawing firm conclusions difficult. Treatment for BHT involves eliminating any predisposing issues and practicing scrupulous oral hygiene. Drug therapy and physical removal of the elongated filiform papillae are available for resistant cases. Clinicians should be aware of the prevalence, the predisposing factors and drug classes that may play a role in the development, and the treatment of BHT.