Schistosomiasis (bilharzia) is a parasitic infection caused by the blood fluke of phylum Platyhelminthes, recognized for significant morbidity in endemic areas.1,2 We present a case of a patient with colonic polyp as the only manifestation of chronic Schistosoma infection.
A 62-year-old woman, originally from Southeast Asia, underwent colonoscopy for cancer screening. On colonoscopy, a subtle, slightly elevated, nearly circumferential polyp was identified in the rectosigmoid colon, extending from 8 to 15 cm from the anal verge. Lesion margins were best visualized using narrow band imaging. Endoscopic appearance was most suggestive of a serrated adenoma. However, submucosal injection with methylene blue and saline revealed uncharacteristic small yellow nodules on the mucosa of the polyp (Figure 1). Furthermore, endoscopic mucosal resection (EMR) revealed extensive submucosal fibrosis. The entire polyp was removed through piecemeal EMR (Figure 1). The patient recovered well and did not report any adverse events.
Histopathology revealed features consistent with a hyperplastic polyp but with numerous calcified Schistosoma eggs in the muscularis mucosa and submucosa, surrounded by dense fibrosis, consistent with chronic intestinal schistosomiasis (Figure 2). The patient will follow with her primary physician for treatment and is due for surveillance colonoscopy in 6 months.
Polyp formation in intestinal schistosomiasis is believed to arise from granulomatous inflammation.3 Egg deposition in the colonic submucosa generates a cellular immune response leading to inflammation and necrosis, which heals by fibrosis and causes hypertrophy of the muscularis. Increasing numbers of ova traveling from the vasculature to intestinal lumen are entrapped by the hypertrophic, fibrous foci, causing foreign body reaction, progressive inflammation, and nodular changes, eventually giving rise to the polypoid appearance of the involved mucosa.
On endoscopy, bilharzial colon polyps can mimic serrated polyps, but these polyps may have yellow mucosal nodules, as observed in this patient during EMR. As opposed to most hyperplastic or serrated polyps, we noted significant submucosal fibrosis during endoscopic resection, presumably secondary to the inflammatory fibrotic reaction. Schistosomiasis manifesting solely as colon polyps without associated gastrointestinal symptoms has not been previously reported. In our case, the patient was completely asymptomatic, and the diagnosis of bilharzial infection was exclusively based on histopathologic findings after colon polyp resection.
The long-term implications of bilharzial colon polyps are unknown, but epidemiological studies suggest a strong association between chronic intestinal infection and cancer.4 Additional studies are needed to determine the potential implications of colon polyps associated with chronic intestinal schistosomiasis.
Author contributions: All authors mentioned above contributed to the conception, design, drafting, finalizing, and approving the final manuscript in order of appearance and meet the ICJME criteria for authorship. All authors are willing to accept accountabilities for all aspects of the manuscript. A. Farooq and A. Hussain reviewed the literature and drafted the original manuscript under the guidance of D. Yang and colleagues K. Kadkhodayan, M. Arain and M. Hasan who provided the case and endoscopic images, reviewed, and edited the final manuscript. C. Singh provided the pathology photomicrographs and brief histology findings. D. Yang is the article guarantor.
Financial disclosure: None to report.
Informed consent was obtained for this case report.
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