<s>[INST] context: Whipple disease A gram-positive actinomycete, named Trophyrema whippleii, is responsible for Whipple disease. Clinical symptoms occur because organism-laden macrophages accumulate within the small intestinal lamina propria and mesenteric lymph nodes, causing lymphatic obstruction- resulting in malabsorptive diarrhoea due to impaired lymphatic transpo. Morphological hallmark- dense accumulation of distended, foamy macrophages in the small intestinal lamina propria. The macrophages contain periodic acid-Schiff (PAS)-positive, diastase-resistant granules that represent lysosomes stuffed with paially digested bacteria. Intact rod-shaped bacilli can also be identified by electron microscopy. Distension of villi due to dense macrophage infiltrates, impas a shaggy gross appearance to the mucosal surface. In Whipple disease, bacteria-laden macrophages can accumulate within mesenteric lymph nodes, synol membranes of affected joints, cardiac valves, the brain, and other sites. Findings typically seen in celiac disease such as intraepithelial lymphocytosis and villous atrophy are not specific for celiac disease and can be present in other diseases, including viral enteritis. Therefore, a combination of histology and serology is most specific for diagnosis of celiac disease. [/INST] question: An intestitinal biopsy is most diagnostic in which of the following conditions? | options: A: Celiac disease B: Tropical sprue C: Whipple disease D: Lactose intolerance | answer: C </s>