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 Frontiers Case report: Melanosis coli combined with colon cancer, causality or coincidence? a Melanotic macule at the wetdry line of the lower lip. b Melanotic Download Scientific Diagram Melanosis coli Wikipedia Melanosis coli is dark brown black pigmentation of colorectal mucosa associated with chronic use of laxatives containing anthraquinone. Examples of such laxatives include senna and rhubarb derivatives. Clinical Importance: There is no association