Functional and morphological abnormalities of the small intestinal mucosa in pernicious anemia--a prospective study.

Small intestinal mucosal function and structure was investigated in 13 patients with pernicious anemia prior to and after treatment with vitamin B12. Histological abnormalities of the jejunal mucosa were shortening of villi of varying degree, increased infiltrate of the lamina propria with monocytes and plasma cells and megalocytosis of the absorptive epithelial cell. Malabsorption of d-xylose occurred in 45%, fat in 30%, vitamin B12-IF complex in 69%, hypocarotinemia in 23% and hypoalbuminemia in 30% of the patients. By contrast, digestive brush border enzymes, i.e. disaccharidases, alkaline phosphatase and leucyl-naphthylamidase were not altered in pernicious anemia. Patients with significant jejunal mucosal abnormalities and decrease of the absorptive surface demonstrated malabsorption of one or more nutrients. Morphological and functional abnormalities were restored to normal after treatment with vitamin B12, suggesting that small intestinal changes in pernicious anemia constitute primary systemic manifestations.