Olanzapine-Induced Black Hairy Tongue During Treatment of Hebephrenic Schizophrenia Decompensation: A Rare Case Report and Brief Review of the Literature.

Black hairy tongue (BHT) is a benign, self-limiting, and usually asymptomatic condition, characterized by abnormally hypertrophied and elongated filiform papillae on the surface of the tongue. In this article, we present the case of a woman diagnosed with hebephrenic schizophrenia who developed BHT after using olanzapine to treat an acute episode of the disease. The temporal coincidence between the development of BHT and the increase in olanzapine dosage to 20 mg daily suggests a likely dose-dependent relationship, making this psychotropic drug the most probable cause of this condition. Although its etiology remains undefined, several factors have been suggested, namely antipsychotics and cannabinoids, likely due to the xerostomia they induce. In this patient, BHT was successfully treated by improving oral hygiene and discontinuing the use of olanzapine and cannabinoids.