Tropical sprue is a malabsorption syndrome.
Tropical sprue occurs chiefly in the Caribbean, southern India, and Southeast Asia, affecting both natives and visitors. The illness is rare in visitors spending < 1 month in areas where the disease is endemic. Although etiology is unclear, it is thought to result from chronic infection of the small bowel by toxigenic strains of coliform bacteria. Malabsorption of folate and vitamin B12 deficiency results in megaloblastic anemia. Tropical sprue has rarely been reported in the US, and the incidence worldwide has been decreasing in recent decades, perhaps because of increasing use of antibiotics for acute traveler’s diarrhea.
Patients commonly have acute diarrhea with fever and malaise. A chronic phase of milder diarrhea, nausea, anorexia, abdominal cramps, and fatigue follows. Steatorrhea (foul-smelling, pale, bulky, and greasy stools) is common. Nutritional deficiencies, especially of folate and vitamin B12, eventually develop after several months to years. The patient may also have weight loss, glossitis, stomatitis, and peripheral edema.
Tropical sprue is suspected in people who live in or have visited areas where the disease is endemic and who have megaloblastic anemia and symptoms of malabsorption. The definitive test is upper gastrointestinal endoscopy with small-bowel biopsy. Characteristic histologic changes (see Table: Small-Bowel Mucosal Histology in Certain Malabsorptive Disorders) usually involve the entire small bowel and include blunting of the villi with infiltration of chronic inflammatory cells in the epithelium and lamina propria. Celiac disease and parasitic infection must be ruled out. Unlike in celiac disease, anti-tissue transglutaminase antibody (tTG) and anti-endomysial antibody (EMA) are negative in patients with tropical sprue.
Additional laboratory studies (eg, complete blood count; albumin; calcium; prothrombin time; iron, folate, and B12 levels) help evaluate nutritional status. Barium small-bowel follow-through may show segmentation of the barium, dilation of the lumen, and thickening of the mucosal folds. D-xylose absorption is abnormal in > 90% of cases. However, these tests are not specific or essential for diagnosis of tropical sprue.
Treatment of tropical sprue is tetracycline 250 mg orally 4 times a day for 1 or 2 months, then 3 times a day for up to 6 months, depending on disease severity and response to treatment. Doxycycline 100 mg orally 2 times a day can be used instead of tetracycline.
Folate 5 to 10 mg orally once/day should be given for the first month along with vitamin B12 1 mg IM weekly for several weeks. Megaloblastic anemia promptly abates, and the clinical response is dramatic.
Other nutritional replacements are given as needed. Relapse may occur in 20%. Failure to respond after 4 weeks of therapy suggests another condition.