Tropical Sprue

I. Introduction

• Chronic diarrheal disease with malabsorption in tropical regions
• Affects small intestinal mucosa, impairing folate and B12 absorption
• Etiology unknown; often follows an infection
• Diagnosis by exclusion of other malabsorption causes

II. Epidemiology

• Incidence up to 29% in tropical countries
• Common in Haiti, Dominican Republic, Puerto Rico, Cuba; rare in Jamaica, Bahamas
• Prevalent in India; less so in Southeast Asia
• Uncommon in Africa, China, Middle East
• Affects residents and travelers staying >1 month
• Severity varies regionally (e.g., milder in northern India)

III. Pathogenesis and Etiology

• Follows acute diarrheal illness; some progress to chronic Tropical Sprue
• Multifactorial: gut dysbiosis, SIBO, immune dysregulation, villous atrophy
• Bacterial toxins/metabolites (acetate, formate) cause inflammation
• Protozoa/fungi: Cryptosporidium, Isospora, Blastocystis, Cyclospora
• Viral particles found in feces (orthomyxo-/coronaviruses)
• Disaccharidase deficiency → carbohydrate malabsorption
• Bile acid deconjugation → fat malabsorption
• Folate/B12 deficiency → megaloblastic anemia
• Vitamin D and magnesium deficiency → hypocalcemia, hypophosphatemia

IV. Clinical Features

• Starts with acute watery diarrhea, fever, malaise
• Progresses to chronic diarrhea, weight loss, fatigue
• Steatorrhea (10–40 g/day), bulky foul-smelling stools
• Signs of vitamin deficiency: glossitis, cheilitis, pallor, night blindness, ataxia
• B12 deficiency: neuropathy, spinal cord degeneration
• Rare: tetany, carpopedal spasm (hypocalcemia)
• Hypoalbuminemia → abdominal distension, pedal edema

V. Differential Diagnosis

A. Malabsorption Syndromes

B. Other Conditions

• Helminths/protozoa: Giardia, Strongyloides, Isospora
• Intestinal TB, SIBO, Crohn disease, chronic pancreatitis
• Immunodeficiency syndromes, SI lymphoma

C. Villous Atrophy Differential

• TS, SIBO, Crohn disease
• Milk/soy protein enteropathy, eosinophilic gastroenteritis
• Autoimmune enteropathy, infections (Giardia, Cryptosporidium)
• AIDS, CVID, malnutrition, Whipple disease

VI. Diagnosis

• Exclude other causes of diarrhea/malabsorption
• Stool tests: ↑ fecal fat, ↓ pH
• Blood: megaloblastic anemia, pancytopenia, hypoalbuminemia, ↓ vitamin D
• D-xylose test: often abnormal
• Barium studies: mucosal thickening, fluid retention
• Endoscopy: duodenal fold flattening, scalloping
• Histology: blunted villi, elongated crypts, ↑ lymphocytes/plasma cells/eosinophils

VII. Treatment

• Tetracycline 250 mg QID + folic acid 5 mg/day for 3–6 months
• Alternative: sulfonamides
• Vitamin B12: 1,000 μg IM weekly
• Iron and folate supplementation
• Nutritional support: enteral/parenteral, medium-chain triglycerides
• Electrolyte correction and hydration