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Secondary syphilis more common in MSM who practice receptive anal intercourse
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Study findings showed that cases of secondary syphilis are more common among men who have sex with men, or MSM, who practice receptive anal intercourse compared with MSM who practice insertive anal intercourse, revealing a population subset that may require additional screening strategies, researchers said.
According to Vincent J. Cornelisse, PhD, adjunct research associate at Monash University in Melbourne, Australia, and colleagues, this trend is potentially due to the difficulty of identifying syphilitic ulcers in the anal canal.
“This hypothesis is consistent with the observation in heterosexuals, where men present most commonly with primary syphilis and women present more commonly with secondary syphilis, presumably because cervical and vaginal chancres are easily missed,” Cornelisse and colleagues wrote.
They conducted a retrospective analysis of MSM aged 16 years or older who were diagnosed with primary or secondary syphilis at the Melbourne Sexual Health Centre between 2008 and 2017.
The analysis included 559 MSM diagnosed with syphilis, of which 338 were primary infections and 221 were secondary. According to the study, 24% of the men reported not practicing receptive anal intercourse. Of the men with primary infections, 73.1% presented with a penile chancre, whereas 22.8% presented with an anal chancre.
The data showed that 92% of MSM with primary syphilis who did not practice receptive anal intercourse presented with penile chancres, whereas 73% of MSM who exclusively practiced receptive anal intercourse presented with anal chancres.
After adjusting for age, HIV status and condom use, MSM who reported practicing receptive anal intercourse were more likely to present with a secondary infection compared with primary infections (adjusted OR = 3.90; P < .001).
“These data suggest that sexual positioning predicts the site of primary infection, and that when primary syphilis occurs at the anus it is often not recognized by the patient, resulting in delayed presentation and treatment,” Cornelisse and colleagues wrote.
“This study highlighted the need to improve early detection of syphilis in MSM who practice receptive anal intercourse, to shorten the duration of syphilis infectivity, and hence to improve syphilis control. We postulate that perhaps the most practical strategy to improve early detection would be to recommend weekly self-[digital anorectal self-examination] for all MSM who practice receptive anal intercourse with [casual sexual partners]. This strategy needs further investigation to determine acceptability, effectiveness and optimal screening frequency.” – by Marley Ghizzone
Disclosures: Cornelisse reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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Matthew Hamill, MBChB, PhD, MPH, MSc
Primary and secondary syphilis (the most infectious early stage of the disease) diagnoses are increasing, particularly in MSM. This study described an association between sexual positioning (who is “top” [ie, inserts their penis into the anus of their sex partner] and who is “bottom” [ie, into whose anus the penis is inserted]) and stage of syphilis in a large sample of Australian MSM. Those who were top were more likely to be diagnosed with primary syphilis, and those who were bottom more likely to be diagnosed with secondary syphilis. It is thought that those who bottom have primary syphilis lesions in the anus and that these lesions go undetected. They are then diagnosed only if and when they go on to develop features of secondary syphilis weeks or months later.
Primary and secondary syphilis are highly infectious. Primary syphilis increases the risk for HIV transmission. These findings are important because primary syphilis is clinically evident before secondary syphilis. If primary syphilis is recognized, the patient can be treated earlier, preventing complications and onward spread to sex partners. MSM whose sexual position is bottom may not be aware of primary syphilis lesions within the anus/rectum because they are not painful, so these lesions will go unnoticed. Men whose sexual position is top overwhelmingly have primary lesions on their penises, which they notice and seek medical help.
Further research is needed to evaluate the role of anal/rectal self-examination by patients who bottom so that they can ‘feel’ the primary lesions and so present for medical evaluation.
This is an excellent retrospective analysis that might well change health promotion messages to individuals who have receptive anal sex.
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