Praziquantel for a Polyp?

Abstract

Schistosomiasis is the second leading cause of parasitic morbidity in the world after malaria, with five known species associated with human infection. Of these five, Schistosoma japonicum is endemic to East Asia and the Philippines, and implicated in colorectal carcinoma. We report a case of incidental colon polyps containing calcified S. japonicumeggs in an otherwise healthy man. This case highlights the asymptomatic presentation seen in the majority of patients with chronic schistosomiasis and lends insight to the pathogenesis of S. japonicum associated colorectal cancer. A 75-year-old asymptomatic man presented to his physician for routine care. His colonoscopy in 2008 was normal and he was referred for interval screening. His medical history was non-contributory. He was born in the Philippines, but moved to the United States in his twenties. He returned annually to the Philippines. He reported child-hood exposure to fresh water lakes, but denied subsequent exposure. His physical examination and laboratory studies were normal. Colonoscopy demonstrated two 2-millimeter flat sessile polyps in the cecum which were removed by cold biopsy (Figure 1). Pathology revealed benign colonic mucosa with calcified S. japonicum eggs focally in the lamina propria and predominantly in the submucosa without an associated inflammatory reaction (Figures 2 and 3). Subsequent Schistosoma species IgG antibody was negative. He was treated with praziquantel and remained asymptomatic at routine follow up. The life cycle of schistosoma involves infectious forms of the parasite passing between snails and humans. Acute infection may cause systemic symptoms and abdominal pain. Chronic infection may lead to portal hypertension, chronic diarrhea, or infect the central nervous, urinary or pulmonary systems. However, the majority of patients are asymptomatic, increasing their risk for malignancy due to prolonged untreated infection. S. japonicum is the only species strongly associated with colorectal cancer, likely due to the high volume of egg production of this species. The imbedded eggs cause an inflammatory reaction with associated risk of dysplasia. Despite this risk, there are no guidelines on appropriate interval for repeat colonoscopy in patients with S. japonicum related polyps. However, literature supports treatment with praziquantal in all patients infected with s. japonicum regardless of chronicity or symptoms based on malignancy risk.1562_A Figure 1. Cecal polyps1562_B Figure 2. Calcified eggs of schistosomiasis in the colonic mucosa and submucosa with overlying normal glandular epithelium. No dysplasia is present. (100X)1562_C Figure 3. Higher magnificent of the calcified eggs. There is no associated inflammatory reaction. (400X)