Underestimated Amoebic Appendicitis among HIV-1-Infected Individuals in Japan

Abstract

Entamoeba histolytica is not a common causative agent of acute appendicitis. However, amoebic appendicitis can sometimes be severe and life threatening, mainly due to a lack of awareness. Also, its frequency, clinical features, and pathogenesis remain unclear. The study subjects were HIV-1-infected individuals who presented with acute appendicitis and later underwent appendectomy at our hospital between 1996 and 2014. Formalin-fixed paraffin-embedded preserved appendix specimens were reexamined by periodic acid-Schiff (PAS) staining and PCR to identify undiagnosed amoebic appendicitis. Appendectomies were performed in 57 patients with acute appendicitis. The seroprevalence of E. histolytica was 33% (14/43) from the available stored sera. Based on the medical records, only 3 cases were clinically diagnosed as amoebic appendicitis, including 2 diagnosed at the time of appendectomy and 1 case diagnosed by rereview of the appendix after the development of postoperative complications. Retrospective analyses using PAS staining and PCR identified 3 and 3 more cases, respectively. Thus, E. histolytica infection was confirmed in 9 cases (15.8%) in the present study. Apart from a significantly higher leukocyte count in E. histolytica-positive patients than in negative patients (median, 13,760 versus 10,385 cells/μl, respectively, P = 0.02), there were no other differences in the clinical features of the PCR-positive and -negative groups. In conclusion, E. histolytica infection was confirmed in 9 (15.8%) of the appendicitis cases. However, only 3, including one diagnosed after intestinal perforation, were diagnosed before the present analyses. These results strongly suggest there is frequently a failure to detect trophozoites in routine examination, resulting in an underestimation of the incidence of amoebic appendicitis.

A Review of the Global Burden, New Diagnostics, and Current Therapeutics for Amebiasis

“…Appendicitis was noted in up to 15% of Japanese HIV-infected patients presenting with appendicitis and undergoing appendectomy [ 38 ]. The only distinguishing feature was a higher median neutrophil count in those with amebic infection compared with those without in this series [ 38 ]. Ameboma, the development of tumor-like granulation tissue in the colonic lumen, can mimic colonic cancer.…”

Seroprevalence ofEntamoeba histolyticaat a voluntary counselling and testing centre in Tokyo: a cross-sectional study

“…In contrast to our seroprevalence data, the national surveillance data of Japan from NESID pragmatically show that the annual number of diagnosed cases of amebiasis (1151 in 2016) is not only much lower than that of syphilis (4575 cases), it is also lower than that of HIV-1 (1443 cases) 22 23. Our results suggest that the endemicity of amebiasis in Japan is currently underestimated, thereby remaining a neglected disease in Japan despite frequently reported life-threatening cases of amebiasis 24–27. Interestingly, in this study, all individuals who were seropositive for E. histolytica were HIV-1 negative, whereas regression analysis identified that seropositivity for syphilis by TPHA was an independent risk factor of a positive result for anti- E. histolytica antibody.…”

Amebiasis Presenting as Acute Appendicitis: Case Report

“…In a Japanese contribution, the amebic element was complicated by HIV-1-infection [6]. This was not the issue in our case.…”