tropical sprue
Summary
Tropical sprue is a malabsorption syndrome of unclear etiology (likely infectious, possibly bacterial overgrowth) that occurs in residents or visitors of tropical regions (Caribbean, India, Southeast Asia). It causes villous atrophy predominantly affecting the jejunum and ileum, leading to malabsorption of nutrients, especially folate and vitamin B12. It responds to antibiotics (tetracycline) and folic acid supplementation.
Detail
Tropical sprue is a chronic malabsorptive disorder that develops in individuals living in or having traveled to tropical areas, typically presenting after acute diarrheal illness. The exact cause is unknown but is thought to involve chronic bacterial infection/overgrowth (e.g., enterotoxigenic E. coli, Klebsiella) that damages the small intestinal mucosa, leading to partial villous atrophy and crypt hyperplasia—histologically similar to but less severe than celiac disease, and it can affect the entire small bowel including the ileum (unlike celiac disease which spares the ileum).
Pathophysiology: Chronic mucosal inflammation reduces the absorptive surface area, impairing absorption of fats, carbohydrates, and vitamins, especially folate and vitamin B12 due to ileal involvement. This leads to macrocytic megaloblastic anemia.
Clinical features: Chronic diarrhea, steatorrhea, weight loss, abdominal distension, and fatigue. Nutritional deficiencies can cause glossitis, anemia (megaloblastic due to B12/folate deficiency), and other signs of malabsorption (e.g., edema from protein loss, bone pain from vitamin D deficiency).
Diagnosis: Made clinically in patients with chronic diarrhea and malabsorption after travel to or residence in an endemic area, along with laboratory evidence of nutrient deficiencies (low folate, B12) and small bowel biopsy showing partial villous atrophy, elongated crypts, and inflammatory infiltrate. Distinguishing from celiac disease is important; tropical sprue does not resolve with gluten withdrawal and typically responds to antibiotics.
Treatment: Prolonged course of antibiotics (tetracycline or doxycycline) for 3-6 months combined with folic acid and vitamin B12 supplementation usually leads to resolution of symptoms and mucosal healing.
High-yield boards points: - Contrast with celiac disease: tropical sprue affects the ileum (leading to B12 deficiency) whereas celiac disease is limited to the duodenum/proximal jejunum. - Occurs after travel to endemic tropical areas. - Responds to antibiotics + folate, unlike celiac disease which responds to gluten-free diet. - Presents with macrocytic anemia due to combined folate/B12 deficiency.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- UpToDate: Tropical sprue
- Harrison's Principles of Internal Medicine
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