24. Dark gingivae

A 32-year-old Caucasian woman was referred for evaluation of the dark colour of her gingivae accidentally found by her dentist during a routine dental check-up. On her intra-oral examination, a diffuse, asymptomatic, symmetrical and dark brown discoloration of both upper and lower gingivae (free and attached) together with areas of brown discoloration of her buccal mucosae and soft palate were seen (Figure 1). The patient has a dark complexion, without areas of discoloration locally, or lymph node enlargement and a clear medical history without drug uptake. She was anxious about her job but has never been a smoker or heavy drinker.

Racial pigmentation is the answer here. This is a very common finding in Afro-Caribbean patients and appears as diffuse hyperpigmentation symmetrically in all parts of the oral cavity but mainly in areas susceptible to trauma, such as gingivae, palate and buccal mucosae. The brown discoloration appears in all gingivae as macules or diffuse brown to black discoloration, with normal margins, due to an increased melanin production of normal melanocytes at the basal layer, as seen in this patient. Smoking melanosis share some clinical features with racial pigmentation, such as the diffused discoloration on gingivae, but differs as its melanosis is restricted mainly in the anterior lower attached gingivae and is related to the amount of tobacco used, disappearing with smoking cessation. Various antimalarial drugs, such as quinacrine, tricyclic antidepressants, oral contraceptives and chemo-therapeutic agents, like busulphan, can produce similar hyperpigmentation, which is resolved when the drug is discontinued. The lack of smoking or drug uptake in this patient excludes smoking or drug-induced melanosis as a possible cause. The patient had never been hypotensive nor had hypotension, hyponatraemia, hypokalaemia and hypoglycaemia – features pathognomonic of Addison's disease, which also causes extensive oral pigmentation. The absence of irregularities of the patient's gingival pigmentation regarding the margins, colour variation, symptomatology or cervical metastasis excludes gingival melanoma from the diagnosis.