A 16-year-old with a history of methamphetamine use presents with diffuse grey-brown pigmentation of the attached gingiva and hard palate. Review of his medications shows long-term acne therapy. The pigmentation is MOST likely caused by:

Correct answer: B. Minocycline

• A. ❌ Methamphetamine causes RAMPANT cervical and interproximal caries ('meth mouth'), xerostomia and bruxism — not mucosal pigmentation.
• B. ✅ CORRECT — MINOCYCLINE produces a characteristic blue-grey to brown pigmentation of the hard palate, attached gingiva, alveolar bone (seen through thin mucosa), teeth, sclera, nails and skin. Long-term acne dosing in adolescents is the classic setting.
• C. ❌ Chlorhexidine causes extrinsic brown staining of TEETH, tongue and restorations, not pigmentation of the attached gingiva and bone.
• D. ❌ Amoxicillin is not associated with mucosal pigmentation.

Note: Other drug pigmentations: antimalarials (chloroquine) → palate · amiodarone, zidovudine, oral contraceptives, chemotherapy agents. Also consider Addison disease and smoker's melanosis.