1542 No Ordinary Colon Polyp: Schistosomiasis

Abstract

INTRODUCTION: Schistosomiasis, is a common parasitic diseases affecting over 200 million people caused by blood flukes of the genus Schistosoma. It is prevalent in tropical areas, particularly in agricultural fishing communities and places with poor water sanitation. Transmission occurs when the cercariae, the infectious form of the parasite, is released from fresh water snails and penetrates human skin. Larvae then mature in the human blood vessels that supply the intestines and genitourinary system. Schistosomiasis commonly involves the intestinal system, it is rare however, for it to present as a large colon polyp. CASE DESCRIPTION/METHODS: A 31-year-old Ethiopian male presented with diffuse abdominal pain and bloody diarrhea for 5 years. A colonoscopy performed 5 years ago at the onset of symptoms was notable only for mild colitis. Due to the persistence of symptoms, he underwent a repeat exam that revealed a normal terminal ileum, cecum, and transverse colon. Mild colitis was seen in the ascending and sigmoid colon. There was moderately severe colitis in the rectum. These areas were biopsied. In addition, a single 2.1 × 2.1 × 1.1 cm pedunculated polyp was found in the sigmoid colon which was removed by snare polypectomy. The polyp was found to contain calcified Schistosoma eggs and worms. The rectal biopsies also showed Schistosoma and multiple calcified eggs. Examination of both the gross and microscopic specimens confirmed the diagnosis of Schistosomiasis mansoni. DISCUSSION: Schistosomiasis affects 10% of the population worldwide and is endemic in Africa, Asia and South America. Patients with Schistosomiasis may present with abdominal pain, bloody diarrhea, anemia, and weight loss as seen in this patient. Endoscopic findings include colitis, mucosal granularity and friability, punctate ulcers, and hemorrhage. Schistosomiasis may also present as an inflammatory polyp. Microscopically, this Th2 cell mediated inflammatory responseis due to the reaction to ova. Worms are known evade the immune response. During the active phase, intense inflammation, granulomas and increased eosinophils can be seen. In the chronic phase, there is less inflammation, however fibrosis, and calcified ova are seen. Calcified eggs, seen in this patient's biopsy, parallels his 5 years of symptoms. Praziquantel is the treatment of choice for schistosomiasis. It is given as a single dose and is most effective four-six weeks after exposure because it does not work on larval forms of Schistosoma. It is curative in 85% of cases.