Gastroenterology Image Challenge: A 57-year-old woman with a past history of aplastic anemia was diagnosed with Crohn’s disease, Montreal A3, L3, B1, in September 2015. The initial endoscopic examination revealed multiple ulcers over the terminal ileum, ileocecal valve, and proximal ascending colon. She received oral mesalazine 4 g/d and prednisolone 2.5–15.0 mg/d during the first year after diagnosis, but did not respond to the treatment; she continued to experience right lower quadrate abdominal pain and intermittent bloody diarrhea. A follow-up colonoscopy showed progressive ulcers over the terminal ileum and ileocecal valve in July 2016.
Given her history of aplastic anemia and sepsis, she hesitated to take azathioprine, methotrexate, or tumor necrosis factor inhibitors. Instead, she started taking indigo naturalis (Qing-Dai) 4.5 g/d in December 2016. She achieved steroid-free clinical remission under the treatment with mesalazine and indigo naturalis. However, a follow-up colonoscopy still revealed a 1.5-cm ulcer over the ileocecal valve in November 2018. In addition, we observed multiple discrete or coalescing irregularly shaped, bluish–black patches from the ileocecal valve to the rectum with a haphazard distribution, reminiscent of the skin markings of Holstein Friesian cattle (Figure A
). A colonic biopsy was obtained, and a representative hematoxylin and eosin stain is shown (Figure B
What is the diagnosis?