We present the case of a 36-year-old man, categorized as MSM (men who have sex with men), with a past medical history of HIV infection under follow-up and syphilis treated in 2018. He presented with a one-month history of anal pain and mild rectal bleeding after bowel movements, occasionally accompanied by fecal urgency. Colonoscopy revealed basal erythema and geographically demarcated ulcers of varying sizes, covered in fibrin, in the distal 10 cm of the rectum (Fig. 1A and B). The largest ulcer measured 7 mm in length (Fig. 1C). Given those findings and the suspicion of an infectious process due to a sexually transmitted infection (STI), biopsy samples were taken for anatomopathologic and microbiologic study. PCR testing detected Chlamydia trachomatis DNA in the rectal ulcer biopsy (Fig. 1D) and IgM and IgA serology was also positive for the pathogen. The anatomopathologic study reported active chronic inflammation of the intestinal mucosa and fragments of granulation tissue. Immunohistochemical staining for cytomegalovirus and herpes simplex virus was negative. Based on the diagnosis of lymphogranuloma venereum-associated proctitis, antibiotic therapy with doxycycline 100 mg every 12 h for 21 days was started, which is the treatment of choice for said infection.

Figure 1.

(A–C) Rectal ulcers with well-defined geographic borders covered by fibrin. Their sizes vary, with the largest measuring 7 mm in length. (D) Superficial ulceration with a moderate mixed inflammatory infiltrate, predominantly acute, composed of polymorphonuclear cells, associated with cryptitis (H&E).

The optical differential diagnosis of proctitis may pose a challenge for the endoscopist. The incidence of STIs has increased over the past decades, accounting for a significant percentage of proctitis cases.1 Clinical manifestations and endoscopic findings may be similar to those of other infectious and inflammatory etiologies, and so STIs should be included as diagnostic options.2,3

Proctitis due to Chlamydia trachomatis may be caused by different serotypes. The serotypes D through K typically produce superficial and asymptomatic infections, whereas the LGV serotypes lead to invasive infections with severe inflammation and systemic symptoms. Clinically, lymphogranuloma venereum progresses in stages, starting with painless rectal or genital ulcers that spontaneously disappear, followed by painful lymphadenopathy and symptoms, such as rectal pain and tenesmus.1 Endoscopically, findings include mucosal inflammation, ulcerations, and mucopurulent exudate, similar to other forms of proctitis. Therefore, diagnosis should be based on clinical suspicion, endoscopic findings, and microbiologic testing, such as the PCR test for Chlamydia trachomatis. Timely antibiotic treatment is crucial for preventing complications and STI education and contact tracing are essential prevention strategies.4