Question

A 45-year-old man presents with chronic diarrhea, significant weight loss, and arthralgia. Endoscopic biopsy of the small intestine reveals numerous foamy macrophages in the lamina propria that stain positive with Periodic Acid–Schiff (PAS). What is the most likely diagnosis?

• A. Tropical sprue
• B. Celiac disease
• C. Whipple’s disease
• D. Giardia infection

Hint:

Always remember to associate the classic triad for Whipple's disease: Chronic Diarrhea, profound Weight loss, and unexplained Arthralgia.
The ultimate diagnostic buzzword to memorize for board exams is the presence of "Diastase-resistant, PAS-positive foamy macrophages" located within the intestinal lamina propria.

Answer 1

The Correct Option is C

Concept:
A middle-aged man presents with a highly classic and syndromic triad consisting of protracted chronic diarrhea, profound unremitting weight loss, and migratory joint pain (arthralgia).
The definitive and pathognomonic diagnostic clue provided in the vignette is the specific histological finding of PAS-positive foamy macrophages densely infiltrating the small intestinal lamina propria, which exclusively points toward a rare, systemic bacterial infection.
Step-by-step Explanation:

• The patient's primary clinical presentation of chronic, high-volume diarrhea coupled with profound, unintentional weight loss strongly signifies the presence of a severe underlying malabsorption syndrome.

• The concurrent presence of systemic migratory arthralgias strongly points towards a widespread systemic etiology rather than an isolated, localized intestinal mucosal issue.

• Whipple's disease is a rare, chronic systemic infection caused specifically by the Gram-positive actinomycete bacterium known as Tropheryma whipplei.

• The classic, textbook clinical tetrad of Whipple's disease includes chronic diarrhea, significant weight loss, prominent arthralgia, and abdominal pain, though neurological and cardiac manifestations can also occur in advanced stages.

• The absolute hallmark diagnostic finding is reliably obtained via an upper gastrointestinal endoscopy combined with a mucosal biopsy of the postbulbar duodenum or the jejunum.

• Detailed histopathological examination of these biopsy specimens consistently reveals a dense, abnormal infiltration of the intestinal lamina propria by enlarged, lipid-laden foamy macrophages.

• Crucially, these specific macrophages contain dense, undigested bacterial degradation products within their lysosomes that stain intensely positive with a Periodic Acid-Schiff (PAS) stain.

• Furthermore, these PAS-positive granules uniquely resist enzymatic digestion with diastase, which differentiates them from simple glycogen deposits.

• Tropical sprue (Option A) and Celiac disease (Option B) are both malabsorptive disorders that typically show varying degrees of villous atrophy and crypt hyperplasia on biopsy, but they entirely lack the pathognomonic PAS-positive foamy macrophages.

• Giardia infection (Option D) is a parasitic infection that would characteristically reveal the classic pear-shaped, flagellated trophozoites visibly adhering to the apical mucosal surface of the enterocytes, not deeply invasive foamy macrophages within the lamina propria.
Final Answer:
The highly specific combination of a malabsorption syndrome, systemic arthralgias, and the histological demonstration of PAS-positive foamy macrophages in the lamina propria is completely diagnostic of Whipple's disease.