The list of possible causes is wide, including coeliac disease, environmental enteropathy (tropical sprue), autoimmune enteropathy, small intestinal bacterial overgrowth, NSAID damage, Helicobacter pylori, other infections and Crohn's disease.
Duodenal lymphocytosis
Anti-gliadin antibodies
Generalized lymphadenopathy
Wandering spleen
Aberrant crypt foci
Black stomach
Pancreatic acinar metaplasia
Tonsil stones