Oral pigmentation in physiologic conditions, post-inflammatory affections and systemic diseases

Melanocytes are found throughout the oral mucosa but usually go unnoticed because of their relatively low level of pigment production. When focally or generally active in pigment production or proliferation they may be responsible for several affections in the oral mucosae ranging from physiologic pigmentation, systemic diseases to malignant neoplasms. The diagnosis of oral pigmentations (OP) is usually challenging for the physician, but a careful examination of the oral cavity may reveal the first manifestation of underlying systemic diseases. Therefore, a full medical history (including drug assumption and smoking) together with a general dermatological examination are mandatory and represent the first approach to OPs. When the diagnosis cannot be reached clinically with enough certainty, a biopsy for histological examination is needed, also in order to exclude possible life threatening conditions such as melanoma. Dermoscopy is another reliable diagnostic tool to make a differential diagnosis between melanocytic lesions and other conditions and then to manage the follow-up of patients. Few papers on the subject have been published in the dermatological literature and the oral cavity is often poorly investigated during routine dermatological examinations. We therefore decided to perform a review of benign OPs, classifying them into diffuse (physiological/racial pigmentations, smoker's melanosis, drug-induced hyperpigmentation, post-inflammatory hyperpigmentation, black hairy tongue, OPs associated to systemic diseases) and localized (amalgam tattoo, melanocytic nevi, melanoacanthoma, melanosis) lesions.