Tropical Enteropathies

Abstract

Purpose of review: The term 'tropical enteropathy' originated in observations in the 1960s that small intestinal morphology and function differed in the tropics from the norms found in temperate climates. It was subsequently shown that this enteropathy is more closely related to environmental conditions than latitude, and it was re-labelled 'environmental enteropathy'. It is now recognised that environmental enteropathy (also now called environmental enteric dysfunction) has implications for the health and linear growth of children in low- and middle-income countries, and it may underlie poor responses to oral vaccination in these countries. The purpose of this review is to define and clarify this enteropathy despite the confusing terminology it has attracted and to contrast it with other enteropathic states.

Recent findings: Recent work has begun to demonstrate the nature of the mucosal lesion and the relationship with microbial translocation which is currently thought to link a failure of mucosal barrier function and the cascade of systemic inflammation which inhibits growth. The evidence is still correlative rather than definitive, but derives some additional support from animal models. There are some common features between environmental enteropathy and other enteropathies, but there are important differences also. The mechanism of the link between enteropathy and vaccine failure is not understood, and neither is it clear how the more severe form of enteropathy, which we refer to as malnutrition enteropathy, is driven by nutrient depletion and intestinal infection. Tropical enteropathies form a group of disorders which include environmental and nutritional enteropathies. The long-term health implications of these disorders for health in low-income countries are just being explored, but the scale of their effects is very large, with millions of people affected.

Keywords: Environmental enteric dysfunction; Environmental enteropathy; Malnutrition; Tropical enteropathy; Tropical sprue.

Fig. 1

Features of enteropathy in a biopsy from a child with severe acute malnutrition. There is an increased inflammatory cell infiltrate in the lamina propria and villus blunting

Fig. 2

High-definition endoscopic images of small intestinal mucosa in EE, demonstrating increasingly severe enteropathic changes. Clockwise from top left: predominant leaves, predominant ridges, predominant convolutions, subtotal villous atrophy

Fig. 3

Confocal laser endomicroscopy of villus structures in environmental enteropathy in a Zambian adult. In contrast to the normal situation, in which fluorescein infected intravenously during the procedure is contained within the mucosa by tight junctions between epithelial cells, fluorescein here is observed leaking from the mucosa