Background
Tropical sprue (TS) is a syndrome characterized by acute or chronic diarrhea, weight loss, and malabsorption of nutrients. It occurs in residents of or visitors to the tropics and subtropics. The first description of tropical sprue is attributed to William Hillary's 1759 account of his observations of chronic diarrhea while in Barbados. Subsequently, tropical sprue was described in tropical climates throughout the world. The definition has been expanded to include malabsorption of at least 2 different substances when other causes are excluded.
View Image | Tropical sprue (H&E, orig. mag. ×10). |
View Image | Endoscopic views of unsuspected celiac disease. A: Absent duodenal folds. B: Mucosal fissures and scalloped folds. C: Scalloped fold. |
The exact causative factor of tropical sprue is unknown, but an intestinal microbial infection is believed to be the initiating insult. The infection results in enterocyte injury, intestinal stasis, and possible bacteria overgrowth. Villous destruction and demonstrable nutrient malabsorption occur in varying degrees. Folate, vitamin B-12, and iron deficiencies are the most common nutrient deficiencies.
Pathophysiology
The exact role of microbial agents in the initiation and propagation of the disease is poorly understood. One theory is that an acute intestinal infection leads to jejunal and ileal mucosa injury; then intestinal bacterial overgrowth and increased plasma enteroglucagon results in retardation of small-intestinal transit. Central to this process is folate deficiency, which probably contributes to further mucosal injury.
Hormone enteroglucagon and motilin levels are elevated in patients with tropical sprue. Enterocyte injury can cause these elevations. Enteroglucagon causes intestinal stasis, but the role of motilin is not clear.
The upper small intestine is predominantly affected; however, because it is a progressive and contiguous disease, the distal small intestine up to the terminal ileum may be involved. Pathological changes are rarely demonstrated in the stomach and colon. Coliform bacteria, such as Klebsiella, E coli and Enterobacter species are isolated and are the usual organisms associated with tropical sprue.[1, 2, 3, 4]
Epidemiology
Frequency
United States
Tropical sprue occurs in geographically limited areas. The syndrome is not reported in US patients unless they have lived in or traveled to any of the areas described below.
International
Tropical sprue occurs in both epidemic and endemic forms, primarily in Southeast Asia and the Caribbean. The actual prevalence of the endemic form is difficult to estimate, but rates as high as 8% are reported in Puerto Rico. One unusual feature is that tropical sprue appears to be limited to certain geographic areas, even within the tropics. For example, although tropical sprue is commonly reported in Puerto Rico and the Dominican Republic, it is not reported in Jamaica. Only a few cases are reported in emigrants from southern Africa.
Mortality/Morbidity
Acute illness complicated by fluid and electrolyte deficits is rarely fatal. The frequency of this complication is not known but appears to be decreasing. Chronic illness with severe malabsorption and anemia can also lead to death, but this usually occurs in patients with comorbid conditions.
Race
Tropical sprue is confined to geographic regions, but it is observed in individuals of all races who live in or visit those regions.
Sex
The male-to-female ratio is equal.
Age
Tropical sprue is primarily an adult disease, but it has been described in children.
Other Tests
Another possible tool to determine gut health may be a noninvasive marker. In a small Australian study, Ritchie et al reported a novel use of of13 C-sucrose breath test in 36 Aboriginal and non-Aboriginal children to measure enterocyte sucrase activity as a marker of small intestinal villus integrity and function.[8] The investigators simultaneously performed intestinal permeability measurements with the lactulose/rhamnose (L/R) ratio on a timed 90-minute blood test with the13 C-sucrose breath test.
Findings included a significantly decreased absorption capacity in Aboriginal children with acute diarrhea (mean 1.9%; cumulative percentage calculated of dose recovered at 90 min) relative to Aboriginal children without diarrhea (4.1%) or non-Aboriginal children (6.1%).[8] The mean L/R ratio in the Aboriginal children with diarrhea was 31.8, whereas the nondiarrheal Aboriginal children's was 11.4.
Ritchie et al noted a significant inverse correlation between the13 C-sucrose breath test and the L/R ratio and concluded the breath test discrimated "among Aboriginal children with diarrhea, asymptomatic Aboriginal children with an underlying environmental enteropathy, and healthy non-Aboriginal controls."[8] The investigators believe the13 C-sucrose breath test "provides a noninvasive, easy-to-use, integrated marker of the absorptive capacity and integrity of the small intestine and could be a valuable tool in evaluating the efficacy of interventions aimed at improving gut health."[8]
Histologic Findings
The following images are supportive of histopathologic findings of tropical sprue.[9]
View Image | Subtotal villous atrophy (H&E, orig. mag. ×10). |
View Image | Tropical sprue (H&E, orig. mag. ×10). |
Medication Summary
Nutrient replacement to correct deficiencies in patients with tropical sprue often includes folic acid, vitamin B-12, and iron. Antibiotic therapy is also helpful because early eradication of bacterial pathogens can relieve continuing injury to the gut.
Folic acid (Folvite)
Clinical Context:
Water-soluble vitamin used in nucleic acid synthesis. Required for normal erythropoiesis. Typically 5 mg po daily. Corrects megaloblastic anemia resulting from folate deficiency and helps regeneration of intestinal mucosa.
Cyanocobalamin (Vitamin B-12, Crystamine, Cyomin)
Clinical Context:
Water-soluble vitamin essential for normal erythropoiesis. Required for healthy neuronal functions and normal functions of rapidly growing cells. Typically 1000 mcg IM weekly.
Class Summary
Nutritionally essential organic substances used in metabolism. Used in nucleic acid synthesis, required for normal erythropoiesis, and help in regeneration of intestinal mucosa. Patients with tropical sprue commonly have deficiencies of folate and, sometimes, vitamin B-12.
Class Summary
Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.
Class Summary
Patients with anemia may need iron replacement along with folic acid and vitamin B-12.
Author
Rohan C Clarke, MD, Attending Physician, Department of Gastroenterology, JPS Health Systems Hospital
Disclosure: Nothing to disclose.
Coauthor(s)
Lisa Anne Ozick, MD, Attending Gastroenterologist, Leumit Health Clinic, Israel
Disclosure: Nothing to disclose.
Oluyinka S Adediji, MD, MBBS, Consulting Staff, Department of Adult and General Medicine, Health Services Incorporated, Montgomery, Alabama
Disclosure: Nothing to disclose.
Rachael M Ferraro, DO, Internal Medicine Hospitalist, Torrance Memorial Medical Center, Little Company of Mary Hospital
Disclosure: Nothing to disclose.
Sabo B Tanimu, MD, Fellow, Department of Medicine, Division of Gastroenterology, Harlem Hospital Center
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Noel Williams, MD, FRCPC, FACP, MACG, Professor Emeritus, Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada; Professor, Department of Internal Medicine, Division of Gastroenterology, University of Alberta, Edmonton, Alberta, Canada
Disclosure: Nothing to disclose.
Chief Editor
Julian Katz, MD, Clinical Professor of Medicine, Drexel University College of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Manoop S Bhutani, MD, Professor, Co-Director, Center for Endoscopic Research, Training and Innovation (CERTAIN), Director, Center for Endoscopic Ultrasound, Department of Medicine, Division of Gastroenterology, University of Texas Medical Branch; Director, Endoscopic Research and Development, The University of Texas MD Anderson Cancer Center
Disclosure: Nothing to disclose.
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