Colon non tumor
Infectious colitis (specific microorganisms)
Intestinal spirochetosis

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 22 May 2017, last major update May 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Spirochetosis [title] intestine
Cite this page: Spirochetosis of colon. PathologyOutlines.com website. http://pathologyoutlines.com/topic/colonspirochetosis.html. Accessed July 21st, 2017.
Definition / general
  • The presence of filamentous nontreponemal spirochetes Brachyspira aalborgi or Brachyspira pilosicoli, on the surface epithelium of the large intestine or appendix
Essential features
  • Intestinal spirochetosis is more common in the developing world, HIV+ patients and men, especially men who have sex with men (MSM)
  • Generally there are no or minimal endoscopic abnormalities
  • Defined histologically by a distinctive basophilic, fringe-like, end on end attachment of densely packed filamentous spirochetes, B. aalborgi or B. pilosicoli, on the surface epithelium of the large intestine or appendix
  • Generally, infection is noninvasive, but uncommonly invasion occurs; it is also found incidentally in association with adenomatous and hyperplastic polyps, diverticular disease and inflammatory bowel disease
  • Most cases are asymptomatic but cases in children, HIV+ patients and MSM often have diarrhea and abdominal pain and children may also have nausea, weight loss and failure to thrive - some improve without treatment, others with metronidazole
  • In vulnerable patients, other pathogens should be sought
Epidemiology
  • Prevalence based on biopsy findings varies from 11.4 to 32.6% (developing world) to 1.7 to 16% (developed countries); these differences suggest diet or sanitation as a means of transmission
  • In the West, prevalence is up to 62.5% in MSM and HIV+ men, suggesting sexual transmission in some cases
  • B. aalborgi is most common in North America and Western Europe and B. pilosicoli is more common in the developing world
  • These microorganisms are more commonly detected via stool PCR or culture and the significance of this is unclear
  • Intestinal spirochetosis has been implicated in diarrheal illness in pigs, dogs, cats, nonhuman primates and other species
Sites
  • Any part of the large intestine and the appendix may be involved
  • Generally considered to be more common in the distal colon and rectum; however in a recent single institution study from Japan, disease was more common in the right colon (Annals Diagn Pathol 2015;19:414)
Pathophysiology
  • Electron microscopic studies reveal that generally spirochetes embed themselves in the luminal border of colonocytes without invasion
  • The mechanism of diarrhea in noninvasive cases is believed to be related to loss of absorptive surface from loss of microvilli
  • Invasive cases are uncommon and the mechanisms of invasion are unclear
Clinical features
  • Most cases in adult women and heterosexual men are asymptomatic
  • Cases in children, HIV+ patients and MSM often have diarrhea (generally watery) and abdominal pain; children may also have nausea, weight loss and failure to thrive
  • Cases with invasion may have colitis with rectal discharge and bleeding; very rarely invasive cases may be associated with spirochetemia and hepatitis
  • A recent study from Sweden has shown an association with colonic eosinophilia and irritable bowel syndrome (Hum Pathol 2015;46:277)
  • Involvement of the appendix may be asymptomatic, associated with typical acute appendicitis or may be associated with symptomatology without appendiceal inflammation
  • The clinical picture may be complicated by other infections such as syphilis, gonorrhea, amebiasis, cytomegalovirus or other pathogens
Diagnosis
  • Biopsy or resection showing the presence of the nontreponemal spirochetes Brachyspira aalborgi or Brachyspira pilosicoli on the surface epithelium of the large intestine or appendix
Laboratory
  • PCR or culture may detect B. aalborgi or B. pilosicoli in stool, but the significance is unclear
Prognostic factors
  • Symptomatology is more likely in MSM and children
  • Spirochetemia, possibly with hepatitis, is very rare and only described in patients with advanced immunosuppression or multiple comorbidities
Case reports
Treatment
  • Asymptomatic patients are generally not treated
  • Symptomatic patients are generally treated with metronidazole, although symptoms may resolve without treatment
Gross description
  • Generally there are no endoscopic abnormalities or minimal findings such as erythema or erosion
Microscopic (histologic) description
  • A basophilic, fringe-like, end on end attachment of filamentous densely packed spirochetes on the surface epithelium of the large intestine or appendix generally in an otherwise normal study
  • Invasive cases may demonstrate increased IgE+ plasma cells and mast cells
  • A Swedish study reported colonic eosinophilia (Hum Pathol 2015;46:277)
  • Increased intraepithelial lymphocytes and very rarely active inflammation in the setting of advanced HIV have been described
Microscopic (histologic) images

Images hosted on PathOut server:

Images contributed by Elliot Weisenberg, M.D.



Images hosted on other servers:
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Accentuation of luminal border

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H&E, Warthin-Starry


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Warthin-Starry

Positive stains
Differential diagnosis
Board review question #1
What is true concerning intestinal spirochetosis?

  1. It is caused by Treponema pallidum
  2. It is commonly associated with cryptitis and crypt abscesses
  3. It is more common in the developing world and in men who have sex with men
  4. It should always be treated
  5. Nearly all cases are symptomatic
Board review answer #1
C. Intestinal spirochetosis is more common in the developing world and in men who have sex with men suggesting transmission is related to sanitation or diet as well as sexual transmission. It is caused by Brachyspira aalborgi and Brachyspira pilosicoli not T. pallidum. Intestinal spirochetosis is usually asymptomatic and may be an incidental finding in a colon biopsy or appendectomy. Asymptomatic cases should not be treated. It is characterized by a basophilic, fringe-like, end on end attachment of filamentous densely packed spirochetes on the surface epithelium of the large intestine or appendix generally in an otherwise normal study. Active inflammation is rare and usually seen in the context of advance HIV infection.