A 58-year-old man presents with weight loss, diarrhoea, migratory polyarthralgia and intermittent confusion. Duodenal biopsy shows villi distended with foamy macrophages. Which stain and organism confirm the diagnosis?

• A Periodic acid-Schiff positive macrophages containing Tropheryma whipplei ✓
• B Ziehl-Neelsen positive bacilli of Mycobacterium avium complex
• C Grocott silver positive budding yeast of Histoplasma capsulatum
• D Congo red positive amyloid deposits in lamina propria vessels

Explanation

Whipple disease is caused by Tropheryma whipplei, an actinomycete, and shows PAS-positive, diastase-resistant inclusions within foamy macrophages filling the lamina propria. MAC infection in immunocompromised patients gives Ziehl-Neelsen positive acid-fast bacilli, the key distractor. The combination of malabsorption, seronegative arthritis and central nervous system signs is classic for Whipple disease.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.