Infectious colitis


Editorial Board Member: Raul S. Gonzalez, M.D.
Elliot Weisenberg, M.D.

Last author update: 1 August 2016
Last staff update: 10 May 2022

Copyright: 2003-2022,, Inc.

PubMed Search: Syphilis of colon

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Syphilis. website. Accessed December 9th, 2022.
Definition / general
  • Disease of the colon caused by the spirochete Treponema pallidum
Essential features
  • With rare exceptions, syphilis is acquired by direct contact with an active syphilitic lesion during sex; anorectal disease is acquired secondary to receptive anal intercourse
  • The clinical manifestations occur after a variable incubation period
  • The primary stage is usually 1 or more nonpainful chancres associated with regional adenopathy
  • In this setting, secondary syphilis follows and may be associated with proctitis or condylomata lata
  • The secondary stage is followed by an asymptomatic latent stage lasting months to years
  • In the absence of treatment or if the patient is unable to clear the infection, gummas may involve the anorectum or colon as part of late or tertiary syphilis
  • Worldwide, an estimated 12 million new cases of syphilis occur each year
  • In the United States in 2014, 63,450 new cases were reported to the CDC
  • There has been a substantial increase in the number of syphilis cases in the United States over the last 15 years, mainly in MSM; many are HIV+
  • The overwhelming majority of cases are acquired sexually, although there are reports of acquiring the disease through kissing or other close contact
    • Sexual transmission is most likely to occur early in the course of the disease during the primary and secondary stages; typically not transmissible by immunocompetent individuals after 4+ years of infection
    • Condoms protect against infection if contact with areas of active infection are avoided
  • Transplacental infection leads to congenital syphilis
  • Infections transmitted through blood transfusion and accidental inoculation have occurred
  • 2/3 eventually clear their infection without treatment, although they may infect others
Clinical features
  • Spirochetes penetrate mucosa or damaged skin and enter lymphovascular spaces and disseminate
  • In primary syphilis, chancres occur 3 to 90 days (mean 21 days) after contact with an active lesion
    • Chancres are a superficial, nontender ulceration, associated with regional nonpainful lymphadenopathy
    • Have a smooth base and raised edges
    • They may be single or multiple, and up to 2 cm
    • Multiple lesions are more common if HIV+
    • May be inconspicuous or absent, particularly in patients with a prior history of syphilis
    • If inoculum is small, only a bump may develop
    • May become secondarily infected, particularly if oral or anal
    • Many patients have mild proctitis and regional lymphadenopathy
    • Chancres typically heal spontaneously in 3 to 6 weeks, but also as quickly as 1 week or as slowly as 12 weeks
    • Chancres increase the risk of acquiring HIV and other sexually transmitted diseases
    • Anorectal chancres may resemble herpes simplex virus infection, chancroid, condyloma acuminatum, lymphogranuloma venereum, typical and atypical mycobacterial infection, anal fissures, anal fistulas, harmless bumps, ingrown hairs, abrasions and mucosal prolapse syndrome / solitary rectal ulcer
      • They are usually painless and asymptomatic, but some patients may experience pain especially during defecation or constipation
      • Discharge may be present
  • Secondary stage:
    • Secondary or disseminated syphilis develops 2 to 8 weeks after exposure, with myriad possible symptoms that usually includes mucocutaneous lesions and lymphadenopathy
    • 2/3 spontaneous clear their infections
    • The inability of some patients to clear their infection is poorly understood, but likely involves the relatively small number of proteins and lipoproteins on the outer membrane of the spirochete and the change from a cellular (Th1) to a humoral (Th2) immune response on the part of the host
    • Usually, but not always, the chancre is still present
    • Most common symptoms are a rash, variable macular to papular to pustular, that commonly involves the palms and soles; also diffuse lymphadenopathy, fever, lethargy, anorexia, weight loss, pharyngitis, laryngitis and arthralgia
    • Condylomata lata, described as a condylomatous lesion that is moist, raised, smooth, itchy, mucin secreting and often malodorous, may occur
    • In secondary anorectal syphilis, proctitis is common, condyloma lata may occur and inguinal adenopathy is common
    • Other less common manifestations of secondary syphilis include mucous patches, erosions and aphthous ulcers of the mouth and throat, headache, meningismus or meningitis, diplopia, impaired vision, tinnitus, vertigo and involvement of cranial nerves, liver or kidneys
  • Tertiary / latent stage:
    • If disease progresses, the secondary stage is followed by an asymptomatic latent stage that may last for years
    • Occurs 5 to 30 years after initial infection
    • Asymptomatic and only detectable by laboratory studies
    • May progress to primarily affect the ascending aorta and CNS, but gummas (soft, noncancerous growth, which is a form of granuloma), may be found in many locations including the anorectum
    • Usually subdivided into neurosyphilis, cardiovascular syphilis, gummatous syphilis and syphilitic (or luetic) osteitis
      • Gummatous syphilis, also known as late benign syphilis, may occur anywhere, but most commonly in bone, skin and mucocutaneous tissue; rarely seen in contemporary medical practice
  • Diagnosis
    • Since T. pallidum has never been successfully cultured on artificial media, diagnosis depends on (a) direct visualization of the organism in tissue with immunohistochemistry, immunofluorescence or Warthin-Starry stain, (b) dark field examination demonstrating spirochetes from an active lesion, (c) PCR testing or (d) serologic testing
    • In anorectal biopsies, the histologic findings are nonspecific; appropriate clinical history and a high index of suspicion are helpful for the pathologist
    • In addition to dark field microscopy, the traditional diagnosis has been serologic testing, with a positive initial screening test for cross reacting nonspecific nontreponemal antibodies (either rapid plasma reagin (RPR) or the venereal disease research laboratory (VDRL) test ), followed by a confirmatory test for specific treponemal antibodies (either fluorescent treponemal antibody (FTA-ABS) or treponema pallidum particle agglutination assay (TPPA))
    • Recently, automated immunoassays (known as the syphilis IgG test, multiplex IgG test or T. pallidum IgG test) have been introduced to detect a specific IgG antibody to syphilis
      • It is now recommended that this be the initial screening test for syphilis and that RPR be the confirmatory test (called reverse sequence syphilis screening)
      • TPPA or FTA-ABS may be also be useful when there was prior treatment of syphilis, low titer RPR, suspicion of a false positive or a strong clinical suspicion of disease
    • PCR testing for syphilis is now available in some laboratories - material obtained from a chancre or other visible lesion as well as peripheral blood may be studied
    • Dark field microscopy of material from an active lesion is available in a limited number of laboratories
    Prognostic factors
    • Disease is generally more severe in immunocompromised patients; these patients also are less likely to clear infection and more likely to relapse during the latent stage
    Case reports
    • Parentally administered benzathine penicillin G (Bicillin LA) is the mainstay to treat all stages of syphilis
    • Treatment varies depending on the stage
    • For penicillin allergy, use doxycycline, tetracycline or azithromycin, but azithromycin should not be used in MSM, HIV+ patients or pregnant women
    • Sex partners should be treated
    Clinical images

    Images hosted on other servers:

    Rectal chancres located
    on posterior wall of rectum
    and regression

    Microscopic (histologic) description
    • Chancre: has a prominent mononuclear cell infiltrate dominated by plasma cells with scattered histiocytes; also obliterative endarteritis with thickened small vessels due to proliferation of endothelial cells and fibroblasts
    • Syphilis proctitis: has a dense mononuclear cell infiltrate with conspicuous plasma cells, often with cryptitis and crypt abscesses; granulomas (usually small) and obliterative endarteritis may be present; plasma cells may be less prominent
    • Condyloma lata: resembles condyloma acuminatum, with prominent epidermal hyperplasia, more edema, chronic inflammatory infiltrate, but less keratinization, minimal if any koilocytosis
    • Gummas: have caseous necrosis, chronic inflammatory cell infiltrate, obliterative endarteritis
    • Healed gummas: become noncontractile scars with arching fibrosis
    Microscopic (histologic) images

    Contributed by Rhonda Yantiss, M.D. and Raul Gonzalez, M.D.

    H&E: anal condyloma lata

    T. pallidum IHC stain

    Images hosted on other servers:
    Missing Image

    Obliterative endarteritis
    with heavy plasma
    cell infiltration

    For more micro images, see Penis / scrotum chapter
    Positive stains
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    Image 01 Image 02