The sprue syndromes.
The sprue syndromes, tropical and nontropical sprue, were both described as disease entities in the 1880s and share similar morphological features with varying degrees of villus atrophy of the small intestinal mucosa, and both present clinically with malabsorption. Recent cell kinetic studies of the turnover of the intestinal epithelium in sprue have convincingly demonstrated that the flat mucosa is caused by increased efflux (cell death) with compensatory crypt hyperplasia. The pathogenetic insult in tropical sprue appears to be a persistent overgrowth of the small intestine by enteric pathogens after a bout of turista. The pathogenesis of nontropical sprue is determined by both genetic factors, demonstrated with a strong association with certain HLA haplotypes (B8, DR3, DR7 and DC3) and presumably also environmental events (virus infection?), which render the mucosa susceptible to gluten. The cause of the malabsorption syndrome is multifactorial and results from both intraluminal and cellular events. The digestion of proteins, carbohydrates, and lipids is compromised due to decreased pancreatic and biliary secretion. The absorption of the digestive products is also severely affected due to decreased activity of microvillus enzymes (dipeptidases and disaccharidases) and a presumed reduction in the number of transport carriers. The clinical presentation is identical and the distinction between tropical and nontropical sprue is based on the history (ie, exposure to a tropical environment) and the response to treatment. Tropical sprue is cured by treatment with tetracycline and folic acid, whereas nontropical sprue responds to a gluten-free diet. Nontropical sprue is associated with dermatitis herpetiformis by common genetic and morphological features, and the skin lesions in dermatitis herpetiformis are also responsive to a gluten-free diet. Finally, there appears to be an increased incidence of intestinal malignancies (lymphoma, adenocarcinoma) in nontropical sprue.