Tropical sprue is a malabsorption syndrome Overview of Malabsorption Malabsorption is inadequate assimilation of dietary substances due to defects in digestion, absorption, or transport. Malabsorption can affect macronutrients (eg, proteins, carbohydrates, fats)... read more .
Etiology of Tropical Sprue
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 Megaloblastic Macrocytic Anemias Megaloblastic anemias result most often from deficiencies of vitamin B12 and folate. Ineffective hematopoiesis affects all cell lines but particularly red blood cells. Diagnosis is usually based... read more . 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 Traveler’s Diarrhea Traveler’s diarrhea is gastroenteritis that is usually caused by bacteria endemic to local water. Symptoms include vomiting and diarrhea. Diagnosis is mainly clinical. Treatment is with <... read more .
Symptoms and Signs of Tropical Sprue
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 Folate Deficiency Folate deficiency is common. It may result from inadequate intake, malabsorption, or use of various drugs. Deficiency causes megaloblastic anemia (indistinguishable from that due to vitamin... read more and vitamin B12 Vitamin B12 Deficiency Dietary vitamin B12 deficiency usually results from inadequate absorption, but deficiency can develop in vegans who do not take vitamin supplements. Deficiency causes megaloblastic anemia, damage... read more , eventually develop after several months to years. The patient may also have weight loss, glossitis, stomatitis, and peripheral edema.
Diagnosis of Tropical Sprue
Endoscopy with small-bowel biopsy
Blood tests to screen for consequences of malabsorption
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 test of choice is upper gastrointestinal endoscopy with small-bowel biopsy. Characteristic histologic changes (see Table: Small-Bowel Mucosal Histology in Certain Malabsorptive Disorders 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 Celiac Disease Celiac disease is an immunologically mediated disease in genetically susceptible people caused by intolerance to gluten, resulting in mucosal inflammation and villous atrophy, which causes malabsorption... read more and parasitic infection Approach to Parasitic Infections Human parasites are organisms that live on or in a person and derive nutrients from that person (its host). There are 3 types of parasites: Single-cell organisms (protozoa, microsporidia) Multicellular... read more 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
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.