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{{Tropical sprue}}
{{Tropical sprue}}
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==Overview==
==Overview==
The exact pathophysiology of [[tropical sprue]] is unclear but is thought to be related to [[intestinal]] [[inflammation]] following an episode of [[diarrhea]]. The inflammation damages the [[intestinal villi]] and also result in [[lymphocytosis]] in the intestinal wall. Deficiency of [[lactase]] enzyme in results in [[malabsorption]] of [[carbohydrates]] and the dysfunctional [[enterocytes]] cause [[steatorrhea]].


==Pathophysiology==
==Pathophysiology==
==Histology==
===Pathogenesis===
The histological changes of TS include: Flattening of the villi and small intestinal inflammation which are similar to an [[autoimmune disorder]] Coeliac disease (also known as ''[[coeliac sprue]]''). A complete flattening of the villi on small bowel biopsy is an uncommon finding in TS unlike Celiac disease.
[[Tropical sprue]] leads to villous atrophy which primarily affects the proximal and the distal gastrointestinal tract including the terminal [[ileum]] causing [[Vitamin B12 Deficiency|vitamin B12]] and [[Folate deficiency|folate]] deficiencies. The pathogenesis of [[tropical sprue]] is unclear and multiple theories have been proposed. The pathogenesis of [[tropical sprue]] includes:<ref name="pmid23481053">{{cite journal| author=Ghoshal UC, Kumar S, Misra A, Choudhuri G| title=Pathogenesis of tropical sprue: a pilot study of antroduodenal manometry, duodenocaecal transit time & fat-induced ileal brake. | journal=Indian J Med Res | year= 2013 | volume= 137 | issue= 1 | pages= 63-72 | pmid=23481053 | doi= | pmc=3657900 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23481053  }} </ref>
{| class="wikitable"
*Post infectious [[diarrhea]] theory is the most supported due to:
!Diagnosis
**The occurrence of the disease following an episode of acute [[gastroenteritis]].
!Villous morphology
**Occurrence of the disease in epidemics in rural areas with poor [[sanitation]].
!Findings in Lamina propria
**Susceptibility of visitors from developed countries to endemic regions in developing countries.
!Involved portion of the GI tract
**The frequency of [[small bowel bacterial overgrowth]] in patients with [[tropical sprue]].
|-
***The [[small intestinal bacterial overgrowth]] affects the [[enterocyte]] brush border activity, duodenal morphology causing [[Villous folds|villous]] atrophy and [[lymphocytosis]] in the intestinal cells.
|'''Tropical sprue'''
*Other factors that can result in [[tropical sprue]] include the following:<ref name="BrownBettington2014">{{cite journal|last1=Brown|first1=Ian S.|last2=Bettington|first2=Andrew|last3=Bettington|first3=Mark|last4=Rosty|first4=Christophe|title=Tropical Sprue|journal=The American Journal of Surgical Pathology|volume=38|issue=5|year=2014|pages=666–672|issn=0147-5185|doi=10.1097/PAS.0000000000000153}}</ref>
|Mild to moderate blunting of the villi with an increased number of Intraepithelial lymphocytes.
**Impaired host [[immune]] response results in prolonged [[inflammation]] of the [[small bowel]] affecting the [[enterocyte]] function.
|Increased number of plasma cells and eosinophils.
**Reduced gut defense mechanisms results in increased bacterial overgrowth which damages the [[enterocytes]] and crypt cells leading to intestinal [[Villous folds|villous]] atrophy and eventually chronic [[diarrhea]].
|Ileum > Duodenum > Colon
**[[Bile acid]] deconjugation affects the [[Enterohepatic circulation|enterohepatic]] circulation and causes [[steatorrhea]].
|-
**[[Vitamin B12 deficiency]] can occur if the [[ileum]] is involved and the [[Megaloblastic Anemias|megaloblastic]] change in the intestinal musocal [[epithelium]] results in the formation of dysfunctional [[epithelial]] cells.
|'''Celiac sprue'''
**Slow mouth to [[cecum]] transit due to intestinal stasis promotes small intestinal bacterial over growth and patients with [[tropical sprue]] have higher levels of [[enteroglucagon]], [[peptide YY]], and [[neurotensin]] which decrease the [[motility]] of [[intestine]] all these can predispose to the development of [[tropical sprue]].<ref name="pmid12702046">{{cite journal| author=Ghoshal UC, Ghoshal U, Ayyagari A, Ranjan P, Krishnani N, Misra A et al.| title=Tropical sprue is associated with contamination of small bowel with aerobic bacteria and reversible prolongation of orocecal transit time. | journal=J Gastroenterol Hepatol | year= 2003 | volume= 18 | issue= 5 | pages= 540-7 | pmid=12702046 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12702046  }} </ref>
|Variable, often there is a complete flattening of the villi. Always there is an increased number of Intraepithelial lymphocytes
**Mucosal [[disaccharidase]] deficiency is also a potential cause as patients with [[tropical sprue]] have higher levels of urinary lactuose excretion suggesting a deficiency of [[lactase]] enzyme.
|Plasma cells > Eosinophils > Neutrophils.
* The [[bacteria]] after an episode of [[diarrhea]] damages the [[enterocytes]] resulting in small bowel stasis, bacterial over-growth, reduced gut [[motility]], [[malabsorption]] and loss of [[Folic Acid|folate]] with further damage to the [[enterocyte]]. All these factors contribute to the vicious cycle of events resulting in [[tropical sprue]].
|Duodenum > Ileum.
*Treatment with [[tetracyclines]] eliminates the bacterial overgrowth and supplementation of [[folate]] helps in regeneration of the [[intestinal epithelium]]. The diagnosis of [[tropical sprue]] is confirmed only if the patient responds to treatment with [[tetracyclines]] and [[folate]] supplementation.
|}
 
==Genetics==
People with Aw-19 [[HLA]] haplotype are at higher risk of developing [[tropical sprue]].
 
==Associated Conditons==
There are no associated conditions with [[tropical sprue]].
 
==Microscopic Pathology==
*Small bowel biopsy reveals similar changes as [[Celiac Disease|gluten sensitive enteropathy]].
*The features demonstrated on a [[Duodenum|duodenal]] [[biopsy]] include:<ref name="pmid14278662">{{cite journal| author=SWANSON VL, THOMASSEN RW| title=PATHOLOGY OF THE JEJUNAL MUCOSA IN TROPICAL SPRUE. | journal=Am J Pathol | year= 1965 | volume= 46 | issue=  | pages= 511-51 | pmid=14278662 | doi= | pmc=1920377 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=14278662 }} </ref>
**Incomplete [[Villous folds|villous]] blunting
**Intra epithelial [[lymphocytosis]]
**[[Eosinophilic]] infilteration of the mucosa
 


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
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Latest revision as of 00:30, 30 July 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aravind Kuchkuntla, M.B.B.S[2]

Overview

The exact pathophysiology of tropical sprue is unclear but is thought to be related to intestinal inflammation following an episode of diarrhea. The inflammation damages the intestinal villi and also result in lymphocytosis in the intestinal wall. Deficiency of lactase enzyme in results in malabsorption of carbohydrates and the dysfunctional enterocytes cause steatorrhea.

Pathophysiology

Pathogenesis

Tropical sprue leads to villous atrophy which primarily affects the proximal and the distal gastrointestinal tract including the terminal ileum causing vitamin B12 and folate deficiencies. The pathogenesis of tropical sprue is unclear and multiple theories have been proposed. The pathogenesis of tropical sprue includes:[1]

Genetics

People with Aw-19 HLA haplotype are at higher risk of developing tropical sprue.

Associated Conditons

There are no associated conditions with tropical sprue.

Microscopic Pathology


References

  1. Ghoshal UC, Kumar S, Misra A, Choudhuri G (2013). "Pathogenesis of tropical sprue: a pilot study of antroduodenal manometry, duodenocaecal transit time & fat-induced ileal brake". Indian J Med Res. 137 (1): 63–72. PMC 3657900. PMID 23481053.
  2. Brown, Ian S.; Bettington, Andrew; Bettington, Mark; Rosty, Christophe (2014). "Tropical Sprue". The American Journal of Surgical Pathology. 38 (5): 666–672. doi:10.1097/PAS.0000000000000153. ISSN 0147-5185.
  3. Ghoshal UC, Ghoshal U, Ayyagari A, Ranjan P, Krishnani N, Misra A; et al. (2003). "Tropical sprue is associated with contamination of small bowel with aerobic bacteria and reversible prolongation of orocecal transit time". J Gastroenterol Hepatol. 18 (5): 540–7. PMID 12702046.
  4. SWANSON VL, THOMASSEN RW (1965). "PATHOLOGY OF THE JEJUNAL MUCOSA IN TROPICAL SPRUE". Am J Pathol. 46: 511–51. PMC 1920377. PMID 14278662.

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