Table 1 Conditions associated with mucosal pigmentation that should be considered during the differential diagnosis of oral melanosis [1, 6, 25,26,27]

Environmental causes

 Smoking-associated melanosis

 Heavy metal pigmentation due to metallic deposit

 Dental amalgam tattoos

 Drug-induced pigmentation

Physiological causes

 Physiological ethnic and/or racial pigmentation

 Labial melanotic macule

 Oral melanocytic nevi

Pathological causes

 Post-inflammatory deposits of melanin

 Peutz–Jeghers syndrome

 AIDS

 Hemochromatosis

 Addison’s disease

 Laugier–Hunziker disease

 Oral melanoacanthoma

 Pseudo-ochronosis

 Bandler’s syndrome

 McCune–Albright syndrome

 Cowden syndrome

 Neurofibromatosis

 Riehl’s melanosis

 LAMB syndrome (Carney complex)

 Polyostotic fibrous dysplasia syndrome

 LEOPARD syndrome

 Hyperthyroidism

 Nelson’s syndrome

 Melanosis associated with melanoma