Syphilis Presenting As Colorectal Cancer

Introduction: Syphilis has long been known as ‘The Great Imitator’ for its ability to mimic other diseases. Although there has been a resurgence of infectious syphilis in the UK since 2000, reports of syphilitic proctitis (SP) are rare. SP has no pathognomonic clinical characteristics and misdiagnosis can lead to costly interventions and delayed treatment. We present the cases of two men with syphilitic colo-rectal lesions which were initially thought to be cancer.

Case Description: 

Case 1 A 40 year old HIV-positive man who has sex with men (MSM) man presented with diarrhoea, rectal discomfort and frank rectal bleeding. Colonoscopy revealed an ulcerating mass in the proximal sigmoid and three other rectal lesions. Biopsy demonstrated inflammatory tissue only with no evidence of malignancy. At an HIV clinic review treponemal serology indicated active syphilis.

Case 2 A 50 year old HIV-negative MSM presented with a short history of rectal bleeding, change in bowel habit and tenesmus. There was a family history of colorectal cancer. Colonoscopy revealed multiple polypoid lesions with central ulceration. Biopsy demonstrated severe inflammatory cell infiltrates with no evidence of malignancy. By chance, the patient presented himself for a sexual health which revealed positive treponemal serology.

The chance identification of positive syphilis serology prompted repeat analysis of histological specimens which proved their treponemal origin. Syphilis treatment resulted in resolution of all bowel lesions in both patients at follow-up endoscopy.

Discussion:  Syphilis should be considered inl patients, particularly MSM, who present with symptoms suggesting colorectal cancer. Clinicians must have a high index of suspicion with regard to diagnosing syphilis. Specific staining techniques or PCR are required to confirm the diagnosis; this may be missed if syphilis is not considered in the differential diagnosis. Sexual history, with rigorous attention to the time course of symptoms, should help to guide investigations and staging of syphilis.