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Torigoe T et al . Acute fulminant amoebic colitisFigure 1 A giant ulcer covered with necrotic tissue is identified in theperianal region.tibiotics therapy administered at another hospital. On admission,we observed a giant ulcer in the perianal region(Figure 1). A diagnosis of AIDS was made on the basisof serum human immunodeficiency virus (HIV) antigenpositivity and an increased HIV viral load (90 000 RNAcopies/mL); his condition was further complicated bypneumocystis carinii infection. Moreover, cytomegalovirus(CMV) colitis was suspected from the occurrence of severebloody diarrhea and the presence of serum antigenemia.Ganciclovir therapy was initiated without performinga colonoscopy because of patient refusal. However,he developed infected necrosis of the skin around theanus and over the perianal ulcer during therapy. Laboratoryinvestigations revealed the following: white bloodcell count, 7500/mm 3 ; hemoglobin, 9.7 g/dL; platelets,545 000/mm 3 ; and serum C-reactive protein, 13.1 mg/dL.Abdominal computed tomography (CT) revealed anabscess formed due to necrosis and extending fromthe perianal region to the lower rectum (Figure 2). Wetherefore ruled out chances of anus preservation andperformed only end-sigmoidostomy and necrotomy ofthe skin tissue from around the anus to the lower rectum.This was done to avoid excessive surgical invasion becauseof a significant decrease in the CD4-positive lymphocytecount (52 cells/mm 3 ). Macroscopic findings ofthe resected colon revealed multiple deep ulcerations coveredwith yellow necrotic plaques (Figure 3). Histopathologicalexamination of the surgical specimen revealedtrophozoite amoebae that had ingested red blood cells inthe resected colon and necrotic tissue, leading to in a finaldiagnosis of acute fulminant amoebic colitis (Figure 4).Furthermore, the serological test for Entamoeba histolyticawas also positive. Typical cytomegalic intranuclear inclusionbodies were not observed in the endothelial cells ofthe resected specimen. Soon after receiving the pathologicaldiagnosis of amoebiasis, metronidazole therapy wasinitiated. The patient’s postoperative course was uneventfulbecause of intensive care. Antiretroviral therapy wasalso prescribed. The HIV viral load gradually decreasedto below the detection limit of the HIV-RNA assay, andthe CD4-positive lymphocyte count increased to 112cells/mm 3 . On the basis of these findings, proctectomyof the residual rectum was performed 11 mo later.DISCUSSIONAmoebiasis, which is caused by the protozoan Entamoebahistolytica (E. histolytica), is the second most frequentparasitosis worldwide, particularly in tropical and subtropicalareas [7] . Recently, the risk of amoebiasis has alsoincreased in developed countries, particularly amongtravelers returning from endemic areas and homosexualmen, including those with HIV infection [8,9] . Interestingly,13.4%-20.4% Japanese homosexual men test positive foramoebic antibodies [10] . However, acute fulminant amoebiccolitis is uncommon, and Adams et al [11] reported thatacute fulminant colitis developed in only 3% of 3013patients with amoebic colitis in South Africa. The outcomeof this condition is very poor, with a high mortalityrate of 70%-100% [1,2] because of serious complicationslike colonic perforation [3,4] , necrotizing colitis [5] , and toxicmegacolon [12] . Perianal ulcers caused by acute fulminantamoebic colitis, such as that observed in the present case,are very rare and occur in only 0.04% patients [11] . Especiallyin homosexual men, the pathogen can easily invadethe anal epithelium, thus resulting in the formation of aperianal ulcer.Amoebic colitis can be diagnosed by the identificationof E. histolytica in the stool or in colonic tissue removedby colonoscopy. Testing for serum antibodies againstE. histolytica is also useful, with a high sensitivity of 85% [13] .In the present case, we could not perform colonoscopicexamination because the patient did not consent to thisprocedure. He was initially treated by ganciclovir therapyafter CMV colitis was suspected because of the occurrenceof severe bloody diarrhea and the presence ofserum antigenemia; however, he responded poorly to thistreatment. Because the final diagnosis of amoebic colitiswas only made after surgery, metronidazole therapy,which is the standard treatment for amoebic colitis, wasdelayed. It is very difficult to distinguish these two diseasesby nonspecific clinical manifestations, such as diarrhea,abdominal pain, and gastrointestinal bleeding; moreover,a few cases of mixed infection with E. histolytica and CMVhave been previously reported [14-16] . However, it shouldbe considered that amoebic colitis is one of the causesof perianal ulcers in homosexual men. The primary treatmentof amoebic colitis is metronidazole; nevertheless,surgical treatment is necessary in cases of perforativeperitonitis [1,2] , necrotizing colitis [5] , and toxic megacolon [12]despite high mortality and poor prognosis. In the presentcase, the perianal ulcer may have developed as a result ofacute fulminant amoebic proctitis, which may be attributedto homosexuality. Several reports have advocated lessinvasive surgical procedures, such as diverting colostomyor ileostomy and simple closure of the perforation, becauseof the high mortality rate following bowel resectionsurgery [17,18] . On the other hand, resection to resolve theseptic focus and stoma creation should be considered oneof the treatment options, depending on the general statusof the patient [19] . We performed only end-sigmoidostomyand necrotomy of the skin tissue from around the anusWJG|www.wjgnet.com4795 September 14, 2012|Volume 18|Issue 34|