Clinical Gastroenterology and Hepatology
Volume 7, Issue 9 , Page A20, September 2009

Melanosis Coli

  • Dan Li

      Affiliations

    • Division of Gastroenterology, University of California, San Francisco, California
    • Department of Medicine, University of California, San Francisco, California
    • ,
  • L. Walden Browne

      Affiliations

    • Department of Pathology, University of California, San Francisco, California
    • ,
  • Uri Ladabaum

      Affiliations

    • Division of Gastroenterology, University of California, San Francisco, California
    • Department of Medicine, University of California, San Francisco, California

published online 15 December 2008.

Article Outline

 

Screening colonoscopy was performed on a 35-year-old woman whose mother died from colon cancer at age 34. She had life-long constipation and had undergone a right hemicolectomy at age 33 because of cecal volvulus. Physical examination revealed a well-healed surgical scar in the midline of her abdomen and was otherwise unremarkable.

Colonoscopy showed the classic diffuse, darkly pigmented appearance of melanosis coli in the colonic mucosa, which contrasted dramatically with the normal pink ileal mucosa at the ileocolonic anastomosis (Figure A). Histopathology on the surgical specimen from her prior right hemicolectomy showed numerous pigmented macrophages in the lamina propria of the colon (Figure B), and ileal mucosa with underlying prominent lymphoid aggregates but no significant pigment deposition in macrophages (Figure C).

Melanosis coli is a condition characterized by dark pigmentation of the colonic mucosa associated with chronic use of laxatives containing anthraquinone. Anthraquinone can induce apoptosis of colonic epithelial cells, which subsequently are phagocytosed by adjacent macrophages.1, 2 The apoptotic bodies are transformed into lipofuscin pigment in macrophage heterolysosomes, producing brown or black discoloration of the mucosa.1, 2 Melanosis coli is a benign condition that can resolve gradually after laxative discontinuation. Rarely, melanosis also can involve the ileum and jejunum.3, 4 The generally selective involvement of the colon may be owing to conversion of the anthraquinone laxative to its active form by cecal bacteria.

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References 

  1. Walker NI, Bennett RE, Axelsen RA. Melanosis coli (A consequence of anthraquinone-induced apoptosis of colonic epithelial cells). Am J Pathol. 1988;131:465–476
  2. Walker NI, Smith MM, Smithers BM. Ultrastructure of human melanosis coli with reference to its pathogenesis. Pathology. 1993;25:120–123
  3. Banai J, Fenyvesi A, Gonda G, et al. Melanosis jejuni. Gastrointest Endosc. 1997;45:432–434
  4. Won KH, Ramchand S. Melanosis of the ileum (Case report and electron microscopic study). Am J Dig Dis. 1970;15:57–64

 Conflicts of interest The authors disclose no conflicts.

PII: S1542-3565(08)01230-5

doi:10.1016/j.cgh.2008.11.030

Clinical Gastroenterology and Hepatology
Volume 7, Issue 9 , Page A20, September 2009