Development, Disappearance, and Clinical Course of Melanosis Coli: Sex Differences in the Progression of Severity

Melanosis coli (MC) is an acquired colorectal disorder visualized as colonic mucosa pigmentation. Disease severity is confirmed based on MC depth, shape, and coloration, although the clinical course is not fully understood. This study sought to clarify characteristics of MC development and disappearance and to investigate its clinical course and severity. Contributors to MC grade progression were explored. This study reviewed MC cases discovered via colonoscopy at a single institution over a 10-year period. Of all 216 MC cases, 17 developing and 10 disappearing cases were detected. Anthranoid laxative use was a key factor: 29.4% of the developing cases had used such agents before the initial MC diagnosis, whereas 40% of disappearing cases had discontinued anthranoids prior to detection of MC disappearance. Among 70 grade I cases, progression to grade II occurred in 16 cases during a mean follow-up of 3.67±2.1 years (rate of progression=22.8%). Males more commonly showed progressive than stable grade I cases, and the probability of progression was higher for male than for female cases. An association between anthranoid administration and MC presence was presumed, and grade I MC was found to progress in severity over 5 years.