Melanosis coli** Melanosis coli is a benign, reversible condition characterized by brown black pigmentation of the colonic mucosa, most often due to chronic use of anthraquinone laxatives. The discoloration is caused Mucosal melanocytic macules Black and Brown: Non neoplastic Pigmentation of the Oral Mucosa Head and Neck Pathology Springer Nature Link What Caused These Multiple Hyperpigmented Macules of the Mouth?