Macrophages Containing PAS Positive granules and rod_shaped bacilli in small intestinal mucosa are Found in
**Core Concept**
Macrophages containing Periodic Acid-Schiff (PAS) positive granules, along with rod-shaped bacilli, in the small intestinal mucosa, point towards a specific infectious process. This scenario is indicative of Whipple's disease, a rare bacterial infection caused by *Tropheryma whipplei*.
**Why the Correct Answer is Right**
The presence of PAS-positive macrophages in the small intestinal mucosa is a hallmark of Whipple's disease. These macrophages contain large amounts of PAS-positive material, which is actually the bacterial cell wall. The rod-shaped bacilli seen in the macrophages are also *Tropheryma whipplei*. The infection leads to malabsorption and weight loss due to the destruction of mucosal lining in the small intestine. The macrophages containing the bacteria are a result of the body's attempt to phagocytose the bacteria, but the bacteria are able to survive inside the macrophages.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the described histopathological features are not characteristic of Crohn's disease, which typically presents with granulomas and ulcers in the small intestine.
* **Option B:** This option is incorrect because the presence of PAS-positive macrophages and rod-shaped bacilli in the small intestinal mucosa is not typical of giardiasis, which is caused by the protozoan *Giardia lamblia*.
* **Option C:** This option is incorrect because the described histopathological features are not characteristic of celiac disease, which typically presents with villous atrophy and increased intraepithelial lymphocytes in the small intestine.
**Clinical Pearl / High-Yield Fact**
Whipple's disease is a rare but serious bacterial infection that can mimic many other gastrointestinal conditions. It can be diagnosed by small intestinal biopsy showing PAS-positive macrophages and rod-shaped bacilli, and treated with antibiotics.
**Correct Answer:** C. Whipple's disease.