- Author: Rohan C Clarke, MD; Chief Editor: Julian Katz, MD more...
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.
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.
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]
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.
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.
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.
Tropical sprue is confined to geographic regions, but it is observed in individuals of all races who live in or visit those regions.
The male-to-female ratio is equal.
Tropical sprue is primarily an adult disease, but it has been described in children.
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