Black hairy tongue: what is your call?

Differential diagnosis: The differential diagnosis includes a normal tongue that has been stained black by food colourings or bismuth ingestion, oral hairy leukoplakia, pigmented fungiform papillae of the tongue and acanthosis nigricans (Table 1). Oral hairy leukoplakia occurs most often in men who are HIV positive and smoke, and it may involve the ventral and dorsal surfaces of the tongue as well as the gingivae and buccal mucosa. White coloured plaques give the tongue a hairy appearance, which can appear and disappear spontaneously. Pigmented fungiform papillae of the tongue is a benign condition that affects dark-skinned people. The fungiform papillae, which exist primarily at the apex and lateral surfaces of the tongue, become enlarged and hyperpigmented, taking on a dark appearance because of melanin-laden macrophages. Acanthosis nigricans is often associated with malignancy. There is elongation of the filliform papillae on the dorsal and lateral aspects of the tongue that appear as multiple papules that are rarely pigmented, and the lips are usually involved. The answer is (d) lingua villosa nigra (also known as black hairy tongue). This condition is benign and selflimiting, 1 and is characterized by an abnormal black coating on the tongue's dorsal surface just anterior to the circumvallate papillae. Brown, yellow and green discoloration has also been described. The sides and tip of the tongue are rarely involved. Lingua villosa nigra is caused by defective desquamation of the tongue with elongation (up to 18 mm in length) and hypertrophy of the filiform papillae.2