Canadian Association of Pathologists - Case of the Month - March, 2008
Diagnosis:
Schistosomal ova
Microscopic Description:
Focally, within the appendical wall, Schistosomal ova can be identified that are associated with granulomatous inflammation. The latter includes concentric fibrosis around eggs marked with collections of mostly lymphocytes and histiocytes, including multinucleated giant cells.
Additional Media:
See this annotated photograph for clarification.
See a collection of this contributor's photomicrographs on "flickr.com" (note: this link may become inactive at some point in the future).
About Schistosomiasis:
Schistosomiasis, a waterborne trematode infestation, is one of the most widespread parasitic diseases in the world. The most common sites affected by schistosomiasis are the urinary tract, vermiform appendix, liver, large bowel, and female genital tract. Schistosoma mansoni and S. Japonicum usually cause infestation of the large intestine. S. Haematobium is mostly found in the bladder and not usually the gut. S. Mansoni is endemic in Africa, central South America and Caribbean basin. S. Japonicum is found in Japan, China and SE Asia. S. Haematobium is seen in Africa (especially Egypt) and the Middle East. Infection of humans usually occurs via bodily contact with larvae-infected water, at which time the larvae penetrate through the skin into systemic circulation, following which adults form in the liver, from which they migrate to the gut to lay eggs. After ingesting water contaminated by eggs from human feces, snails act as intermediate hosts for larvae development, thus completing the parasite cycle.
Gross pathological changes in the gut include acute proctitis/colitis and various forms of chronic granulomatous infections that can result in ulceration, strictures, pericolic masses, and polyposis. Microscopic appearance of schistosomiasis usually includes chronic inflammatory responses around eggs marked by infiltration with lymphocytes, eosinophils, fibrosis and giant cells. Characteristic concentric fibrosis with granulomatous inflammation is described (see photomicrographs and virtual slides from this case). Eggs sometimes are not associated with an inflammatory response and can be very difficult to detect microscopically. Turner first described schistosomiasis of the appendix in 1909. Appendicular schistosomiasis as a cause of acute appendicitis is a well-defined clinicopathologic entity and has been reported to occur in about 14% of all cases of appendicitis presenting in endemic areas.
References:
- Morson and Dawson's Gastrointestinal Pathology by David W. Day Blackwell Publishing, 2003
- Turner SA. Bilharziasis of the appendix. Trans Mrd J 1909;5:210.
- Weber et al. Schistosomiasis Presenting as Acute Appendicitis in a Traveler. J Travel Med 1998; 5:147-148.
Previous COTMs featuring pathology of the appendix: