An epidemiologic study of children with failure to thrive is undertaken in Guatemala. Some of these children with ages 1 to 3 years have repeated bouts of diarrhea, but do not improve with dietary supplements. Jejunal biopsies show blunted, atrophic villi with crypt elongation and chronic inflammatory infiltrates. What is the most likely factor contributing to recurrent diarrhea in these children?

Environmental enteropathy affects millions of children worldwide. Recurrent infection sets up a cycle of mucosal injury and inflammatory response that produces an appearance similar to celiac disease. There is no single infectious agent implicated, but likely there are many pathogens that cumulatively contribute to mucosal damage. Abetalipoproteinemia is a rare condition from mutations in microsomal triglyceride transfer protein that impairs the enterocyte transport of lipoproteins. Cystic fibrosis results from CFTR gene mutations affecting chloride ion channels, but the resultant diarrhea is primarily from the loss of pancreatic function. The most common disaccharidase deficiency is lactase deficiency, with milk intolerance. NOD2 gene mutations may contribute to Crohn disease.