REV ARGENT COLOPROCT | 2024 | VOL. 35, N

2 CASE REPORT

PRIMARY RECTAL SYPHILIS MIMICKING RECTAL TUMOR Chinelli J. et al..

Primary rectal syphilis mimicking rectal tumor

Javier!Chinelli,!Gusta vo !R o dr íguez

Corporación Médica de Canelones (COMECA). Canelones, Uruguay

ABSTRACT

Introduction: Syphilis is a sexually transmitted disease with a

raising incidence.

Case description: 18-year-old male with an inflammatory rectal

pseudo-tumor. After diagnosis, antibiotic therapy was administered

with uneventful recovery.

Discussion: Rectal syphilis is a rare condition, with particular

endoscopic and imaging findings that allow differentiation from

rectal malignancy. Direct visualization of Treponema pallidum with

immunohistochemistry staining confirms the diagnosis.

Conclusion: Syphilitic proctitis must be suspected among high-risk

patients with atypical rectal tumors. Active management of sexual

partners is crucial for early diagnosis and treatment.

Key words: syphilis, proctitis, pseudo-tumor

INTRODUCTION

Syphilis is an infectious disease caused by the bacteria

Treponema pallidum (spirochete) and is transmitted by

direct contact. Its incidence has increased up to 3 times in

recent years, particularly in men who have sex with men,

whether or not they are carriers of the human immunodefi-

ciency virus (HIV), although the association between both

pathologies is very frequent, up to a 30-40%.

We report a case of primary rectal syphilis (syphilitic procti-

tis), a rare occurrence of the disease, particularly in its

pseudotumoral presentation.

CASE

An 18-year-old male patient, with multiple sexual partners

and unprotected anoreceptive intercourse, with no other

relevant clinical history, consulted for proctalgia, rectal

bleeding, and tenesmus of 2-week duration. The proctologi-

cal examination highlights the absence of perianal lesions

and the digital rectal examination reveals immediately above

the rectal ring a circumferential tumor that bleeds easily,

firm, not very mobile, somewhat painful, whose proximal

edge cannot be reached.

Colonoscopy shows a circumferential thickening of the

rectal wall up to 10 cm from the anal verge, with soft muco-

sa, distensible to insufflation, intensely congestive with

some superficial ulcerations covered with fibrin (Fig. 1A),

mamelonated near the anal canal (Fig. 1B).

Magnetic resonance imaging (MRI) of the pelvis shows

regular and uniform thickening of the rectal wall, hy-

pointense on T2, and multiple mesorectal nodes (Fig. 2).

HIV and VDRL tests were negative, while the endoscopic

biopsy showed the presence of spirochetes using an im-

munohistochemical technique (Fig. 3), confirming the

diagnosis of rectal syphilis.

Treatment was carried out by administering benzathine

penicillin G 2.4 million IU weekly for 3 weeks. There was a

good clinical response with resolution of symptoms and

complete remission of endoscopic lesions. Fig. 4 shows the

endoscopic appearance of the rectum after treatment.

Figure 1. Endoscopic appearance of the rectal lesion. A. Parietal thickening. B. Mamelonated mucosa.

Figure 2. MRI. A. Axial section. B. Sagittal section. Rectal

parietal thickening (white arrows) and mesorectal enlarged

lymph nodes (yellow arrows).

Figure 3. Immunohistochemistry. Spirochetes

are identified (arrows).

The authors declare no conflict of interest. Javier Chinelli: jchinelli01@gmail.com

Javier Chinelli https://orcid.org/0000-0003-2381-697X

REV ARGENT COLOPROCT | 2024 | VOL. 35, N

2 CASE REPORT

PRIMARY RECTAL SYPHILIS MIMICKING RECTAL TUMOR Chinelli J. et al..

Figure 4. Colonoscopy after treatment. Complete remission of the lesions.

DISCUSSION

Sexually transmitted infections represent a global health

problem, with an estimated 374 million cases worldwide,

according to WHO figures from 2020.

In particular, syphi-

lis is a systemic disease with very varied clinical manifesta-

tions, which depending on its evolutionary stage include

ulcerated cutaneous-mucosal lesions, rash, enlarged lymph

nodes and neurological involvement.

After infection through anal sexual contact, the disease may

be asymptomatic or present clinical manifestations between

2 and 10 weeks later. Particularly in the anorectum, ulcers

(syphilitic chancre), proctitis or masses mimicking neo-

plastic tumors can be found.

Lesions can heal after several

weeks even without treatment, giving rise to the second

stage or secondary syphilis, characterized by a palmoplantar

rash, fever, rectal masses and/or condylomata lata, the latter

being extremely contagious. Again, these manifestations

may disappear without specific treatment after 3 to 12

weeks. The majority of patients will evolve to a form of the

disease called “latent” syphilis,

only detectable through

laboratory tests, and 10-15% will present manifestations up

to 20-30 years later, especially neurological ones, which

constitute tertiary syphilis.

The clinical presentation in our patient is the pseudotumoral

form. Some elements of the endoscopic study and MRI

allow us to differentiate this entity from a rectal neoplasia,

such as the presence of intensely inflamed mucosa, parietal

distensibility with insufflation, uniform thickening and

absence of hyperintensity on diffusion images, the latter

typically present in adenocarcinomas and mucinous carci-

nomas.

Even so, diagnostic doubts may persist, especially

to rule out rectal lymphoma, which is why biopsy plays a

fundamental role.

Serological diagnosis is based on the combination of a

treponemal and non-treponemal tests. The usual non-

treponemal test is the VDRL, which was negative in our

patient. This is not uncommon, especially in cases of prima-

ry syphilis. Likewise, there are also false positive results,

particularly when there is HIV co-infection -ruled out in the

patient- or during pregnancy.

Among non-treponemal tests, many are available, such as

the Absorbed Fluorescent Treponemal Antibodies test, but

they are not always used, as other direct diagnostic methods

exist.

In the present case, the diagnosis was made by immuno-

histochemical test from the endoscopic biopsy of the muco-

sa, demonstrating the spirochetes using a chromogen.

Treatment consists of benzathine penicillin G 2.4 million

units intramuscularly, once a week, for 3 consecutive

weeks.

The response is evaluated clinically and by serology, when

it was initially positive. In this case, clinical and endoscopic

control was also performed, which showed complete resolu-

tion of the rectal lesion.

Of equal importance is the tracing and study of possible

contacts to detect the infection early and proceed to treat-

ment, in order to avoid new infections and the progression

of syphilis to late stages, with the morbidity that this entails.

CONCLUSION

Rectal syphilis is a rare entity and should be suspected in the

presence of a rectal mass with atypical characteristics,

especially in high-risk population such as the case analyzed.

Identification of contacts is essential to detect infection in

early stages and provide timely treatment.

ACKNOWLEDGEMENT

We thank Dr. Elisa Laca, pathologist, for the photographic

material provided.

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