A patient presents with chronic diarrhea, weight loss, arthralgia, dementia, and abdominal pain; what condition is suggested by foamy macrophages on PAS staining of jejunal biopsy?

The presence of foamy macrophages on PAS staining in a jejunal biopsy is strongly indicative of Whipple disease. Whipple disease is a systemic illness caused by the bacterium Tropheryma whipplei, which typically leads to malabsorption and inflammatory symptoms in the gastrointestinal tract. The foamy macrophages represent macrophages that have ingested lipid-laden components, specifically lipoproteins, as a result of the infection's effect on the intestinal mucosa.

In Whipple disease, the clinical presentation can vary widely, but the combination of chronic diarrhea, weight loss, arthralgia (joint pain), dementia, and abdominal pain is particularly characteristic. The systemic involvement often includes the central nervous system, which can lead to neurological symptoms such as dementia.

Other listed conditions do not present with foamy macrophages or have different biopsy findings. Celiac disease, for example, is associated with villous atrophy and intraepithelial lymphocytes rather than foamy macrophages. Lactose intolerance generally does not feature such systemic symptoms and is primarily a functional condition due to lactase deficiency, and Crohn's disease would show a different histopathological picture, focusing on granulomas and transmural inflammation rather than the specific lipid-laden macrophages