Pseudomelanosis -Blue-Black Staining of Colon

The image below is from a 57 yo woman with Crohn’s disease who was taking a supplement, indigo naturalis (Qing-Dai). “Higher magnification disclosed bluish, needle-like crystals in the cytoplasm of these histiocytes. In light of the presence of pigment-laden histiocytes, we called the lesions indigo naturalis-related pseudomelanosis. Unlike melanosis coli, which typically shows continuous homogeneous brown or black discoloration of colon mucosa (snake-skin appearance or starry sky appearance), indigo naturalis-related pseudomelanosis exhibits a haphazard distribution of black discoloration reminiscent of the skin markings of Holstein Friesian cattle…It remains to be seen whether deposition of indigo naturalis has any long-term adverse effect, although histologically the mucosa with indigo deposition was not accompanied by significant inflammatory activity.”

Link: P-H Le et al. Gastroenterol 2021; 161: e10-e11. Colonic Bluish–Black Patches in a 57-Year-Old Woman with Crohn’s Disease