Black discoloration of the tongue should be distinguished from black “hairy” tongue, also known as lingua villosa nigra, characterized by hypertrophy or hyperkeratosis of the filiform papillae. In the absence of papillary hypertrophy or hyperkeratosis, there are endogenous and exogenous causes of black discoloration of the tongue.1 We describe a 92-year-old woman presenting with a black tongue and positive culture findings for Enterobacter cloacae, and we discuss the duality of chlorhexidine and E cloacae in the pathogenesis of black tongue.
El Sayed F, Dhaybi R, Ammoury A, Bazex J. Black Tongue and Enterobacter cloacae. Arch Dermatol. 2007;143(6):799-816. doi:10.1001/archderm.143.6.815-a