Immunohistochemical detection of chlamydia trachomatis in sexually transmitted infectious proctitis

INTRODUCTION: Since 2003, a progressive increase in sexually transmitted infections (STI), presented as proctitis, has been described in homosexual men. In 2013 Arnold et al. described microscopic features that enable pathologists to formulate a histological diagnosis of STI related proctitis. The aim of this study is to identify the presence of Chlamydia trachomatis by immunohistochemistry in a group of patients with male to male sexual activity and pathology compatible with STI proctitis. METHODS: Cross-sectional study. The study included 54 patients with risky sexual activity and histopathology compatible with STI-proctitis according to Arnold´s recommendations. The Chlamydia trachomatis identification was carried out retrospectively on paraffin blocks using mouse monoclonal antibodies from Santa Cruz biotechnology. RESULTS: all patients were young men with male to male sexual activity, 69% were positive for HIV. The most common endoscopic presentation was rectal ulcer (61%). Basal lymphoplasmacytic inflammation and mild crypt distortion were the most common histological findings. The immunohistochemical study identified positivity for Chlamydia trachomatis in 40% (18 of 45 tested) of STI proctitis cases. DISCUSSION: The epidemiological and endoscopic characteristics of the patients studied are similar to those previously reported. In accordance with Arnold et al., the most common histological findings were (a) mild distortion of the crypts; (b) dense and basal lymphoplasmacytic infiltrate and (c) scarcity of eosinophils. The positivity of chlamydia trachomatis in immunohistochemistry was lower than others studies that used PCR for this purpose. We did not find similar published studies to compare our results. CONCLUSIONS: In summary, 54 cases of patients with STI related proctitis are presented, all of them with distinctive histological characteristics and third of the cases tested positive by IHC for Chlamydia trachomatis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12876-022-02233-w.