GI Path Online
Pathology of Tropical Sprue
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sprue (TS) is a clinical entity of unknown etiology characterized by an
acquired chronic diarrheal illness and malabsorption that affects
indigenous inhabitants and expatriates, either long-term residents or
short-term visitors, in the tropical countries.
Sprue occurs mainly in Asia, including Sri Lanks, Southern India, Malaysia, Indonesia, Hong Kong and China, some Caribbean Islands, Puerto Rico and parts of South America.
Pathogenesis: The exact pathogenetic sequence of Tropical sprue remains incompletely characterized.
Bacterial overgrowth, disturbed gut motility, and hormonal and histopathologic abnormalities contribute to the development of TS in a susceptible host.
Postinfective tropical malabsorption (TM; tropical sprue) starts with an acute intestinal infection (bacterial, viral, or parasitic) which can affect predominantly the small or the large intestine.
Miscellaneous invasive pathogens cause subsequent enterocyte damage affecting the entire small intestine and, to a lesser extent, the colon.
Enteroglucagon, a tropic hormone, is then liberated and reaches a high plasma concentration.
Small-intestinal stasis results.
Further bacterial colonisation (in the lumen and also at the enterocyte surface) is encouraged.
Continuing enterocyte damage is worsened by coexistent folate depletion, which is initiated at the onset of disease; body stores of folate reach a low concentration by 3 or 4 months.
The cycle continues until the bacterial overgrowth is eliminated with an antibiotic (eg, tetracycline), or mucosal integrity recovers (hastened by oral folic-acid supplements), or both.
Clinical presentation: Tropical sprue presents with diarrhea, anorexia, weight loss, and megaloblastic anemia.
Remissions and relapses are a characteristic feature. In severe cases 10 stools or more may be passed daily.
Tropical sprue should be considered in the differential diagnosis of chronic diarrhoea in patients with a history of travel in tropical regions.
The most frequent medical problem that travellers to the tropics experience is diarrhoea with an incidence of 30%.
A small proportion of these patients eventually present with chronic diarrhoea.
At that moment, the relation to their previous travelling may not be immediately clear.
One of the causes of this chronic diarrhoea to be considered is tropical sprue.
Pathological features: Image
Histologically, the intestinal changes range from near normal to severe diffuse enteritis.
The changes closely resemble those of coeliac disease, although they tend to be less advanced.
The partial villous atrophy has been a constant finding.
The jejunal villi are blunted or, rarely, absent and there is a subepithelial infiltration with plasma cells and lymphocytes.
In some cases there is enlargement of the nuclei of epithelial cells.
In severe cases the ileum is also affected.
These changes are associated with malabsorption of fat, protein, carbohydrate and vitamins and the presence of diarrhoea which may lead to depletion of water, electrolytes, iron and calcium.
A macrocytic anemia is common with megaloblastic change in the bone marrow due to folate deficiency.
Vitamin B12 deficiency takes longer to develop.
Mild changes in the jejunal mucosa are common in asymptomatic indigenous peoples, without gross malabsorption, throughout the tropics.
The clinical features and the history of residence in an area noted for tropical sprue will suggest the correct diagnosis if care is taken to recognise the early and the mild case as well as the late presentation.
Evidence of malabsorption should be sought.
Macrocytosis occurs early.
Serum and erythrocyte levels of folate are low.
Anaemia may also be hypochromic from defective absorption of iron.
Jejunal biopsy shows shows partial villous atrophy which is not specific for tropical sprue.
Jejunal mucus and fluid is examined to exclude parasites.
Barium meal and follow through examinations are necessary only to exclude other disease.
Differential diagnosis is from other forms of steatorrhoea.
Additional causes in the tropics are infections of the intestine with Giardia intestinalis, Stongyloides stercoralis or Capillaria philippinensis.
Early symptoms or sprue may errorneously be attributed to amoebiasis.
The response to treatment to tetracycline and folic acid has been uniformly successful.
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