Tropical sprue pathophysiology: Difference between revisions
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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. | 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== | ||
===Pathogenesis=== | ===Pathogenesis=== | ||
Pathogenesis of tropical sprue is unclear and multiple theories are 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> | Pathogenesis of [[tropical sprue]] is unclear and multiple theories are 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> | ||
*Post infectious diarrhea theory is the most | *Post infectious [[diarrhea]] theory is the most supported, due to the occurrence of the disease following an episode of acute [[gastroenteritis]], occurrence of the disease in epidemics in rural areas with poor [[sanitation]], susceptibility of visitors from developed countries to endemic regions and 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 atrophy and lymphocytosis in the intestinal cells. | *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 affects the proximal and the distal gastrointestinal tract including the terminal ileum causing vitamin B12 and folate deficiencies. | *[[Tropical sprue]] affects the proximal and the distal gastrointestinal tract including the terminal [[ileum]] causing [[Vitamin B12 Deficiency|vitamin B12]] and [[Folate deficiency|folate]] deficiencies. | ||
*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> | *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> | ||
**Impaired host immune response results in prolonged inflammation of the small bowel affecting the enterocyte function. | **Impaired host [[immune]] response results in prolonged [[inflammation]] of the [[small bowel]] affecting the [[enterocyte]] function. | ||
**Reduced gut defense mechanisms resulting in increased bacterial over growth damages the enterocytes and crypt cells to cause intestinal villous atrophy. This causes chronic diarrhea. | **Reduced gut defense mechanisms resulting in increased bacterial over growth damages the [[enterocytes]] and crypt cells to cause intestinal [[Villous folds|villous]] atrophy. This causes chronic [[diarrhea]]. | ||
**Bile acid deconjugation affects the enterohepatic circulation and causes steatorrhea. | **[[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 change in the intestinal mucuosal epithelium results in the formation of dysfunctional epithelial cells. | **Vitamin B12 deficiency can occur if the ileum is involved and the megaloblastic change in the intestinal mucuosal epithelium results in the formation of dysfunctional epithelial cells. | ||
**Slow mouth to | **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> | ||
**Mucosal disaccharidase deficiency is also a potential cause as patients with tropical sprue have higher levels of urinary | **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. | ||
* The bacteria after an episode of diarrhea damages the enterocytes: resulting small bowel stasis, bacterial over-growth, reduced gut motility, malabsorption and loss of folate with further damage to the enterocyte. All these factors contribute to the vicious cycle of events resulting in tropical sprue. | * The [[bacteria]] after an episode of [[diarrhea]] damages the [[enterocytes]]: resulting 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]]. | ||
*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. | *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=== | ===Genetics=== | ||
People with Aw-19 HLA haplotype are at higher risk of developing tropical sprue. | People with Aw-19 [[HLA]] haplotype are at higher risk of developing [[tropical sprue]]. | ||
===Microscopic Pathology=== | ===Microscopic Pathology=== | ||
*Small bowel | *Small bowel biopsy reveals similar changes as [[Celiac Disease|gluten sensitive enteropathy]]. | ||
*The features demonstrated on a 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> | *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 blunting | **Incomplete [[Villous folds|villous]] blunting | ||
**Intra epithelial lymphocytosis | **Intra epithelial [[lymphocytosis]] | ||
**Eosinophilic infilteration of the mucosa | **[[Eosinophilic]] infilteration of the mucosa | ||
===Associated Conditons=== | ===Associated Conditons=== | ||
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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
Pathogenesis of tropical sprue is unclear and multiple theories are proposed.The pathogenesis of tropical sprue includes:[1]
- Post infectious diarrhea theory is the most supported, due to the occurrence of the disease following an episode of acute gastroenteritis, occurrence of the disease in epidemics in rural areas with poor sanitation, susceptibility of visitors from developed countries to endemic regions and 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 atrophy and lymphocytosis in the intestinal cells.
- Tropical sprue affects the proximal and the distal gastrointestinal tract including the terminal ileum causing vitamin B12 and folate deficiencies.
- Other factors that can result in tropical sprue include the following:[2]
- Impaired host immune response results in prolonged inflammation of the small bowel affecting the enterocyte function.
- Reduced gut defense mechanisms resulting in increased bacterial over growth damages the enterocytes and crypt cells to cause intestinal villous atrophy. This causes chronic diarrhea.
- Bile acid deconjugation affects the enterohepatic circulation and causes steatorrhea.
- Vitamin B12 deficiency can occur if the ileum is involved and the megaloblastic change in the intestinal mucuosal epithelium results in the formation of dysfunctional epithelial cells.
- 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.[3]
- 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.
- The bacteria after an episode of diarrhea damages the enterocytes: resulting small bowel stasis, bacterial over-growth, reduced gut motility, malabsorption and loss of folate with further damage to the enterocyte. All these factors contribute to the vicious cycle of events resulting in tropical sprue.
- 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.
Microscopic Pathology
- Small bowel biopsy reveals similar changes as gluten sensitive enteropathy.
- The features demonstrated on a duodenal biopsy include :[4]
- Incomplete villous blunting
- Intra epithelial lymphocytosis
- Eosinophilic infilteration of the mucosa
Associated Conditons
References
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ SWANSON VL, THOMASSEN RW (1965). "PATHOLOGY OF THE JEJUNAL MUCOSA IN TROPICAL SPRUE". Am J Pathol. 46: 511–51. PMC 1920377. PMID 14278662.