A patient presents with a photo showing a brown-black discoloration on the dorsal tongue with elongated filiform papillae. The most likely diagnosis is:

Correct answer: B. Hairy tongue (lingua villosa nigra)

• A. Geographic tongue shows migratory, irregular depapillated patches with white borders on the dorsal tongue.
• B. Correct. Hairy tongue (hairy/black tongue) results from elongation and hypertrophy of filiform papillae, often with brown-black discoloration from chromogenic bacteria, tobacco, or coffee. It is associated with antibiotics, poor oral hygiene, and xerostomia.
• C. Median rhomboid glossitis is a smooth, rhomboid, erythematous depapillated area on the dorsal midline tongue.
• D. Hairy leukoplakia appears as white, vertical corrugations on the LATERAL borders of the tongue in immunocompromised patients (HIV); it does not cause elongated papillae or brown-black color.