PAS-positive macrophages in the lamina propria are most characteristic of which condition?

• A. Celiac disease
• B. Giardiasis
• C. Whipple disease
• D. Crohn disease

Answer: (C)

Whipple disease shows infiltration of the intestinal lamina propria by foamy macrophages that are packed with Tropheryma whipplei. These macrophages are strongly positive with periodic acid–Schiff stain, and the staining is resistant to diastase digestion, meaning the PAS positivity remains after enzymatic digestion of glycogen. This combination—PAS-positive, diastase-resistant macrophages in the lamina propria—is the classic histologic hallmark and explains the malabsorption and systemic symptoms. Other conditions can cause intestinal inflammation or malabsorption, but they do not produce this distinctive pattern of diastase-resistant, PAS-positive macrophages in the lamina propria.