WBR0927

Author	[[PageAuthor::Twinkle Singh, M.B.B.S. [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	USMLE Step 1
Main Category	Pathology
Sub Category	Gastrointestinal
Prompt	A 50-year-old man presents with complaints of diffuse abdominal pain and non-bloody diarrhea. He states that he recently experienced joint pains, unintentional weight loss, and decreased night vision over the past few months. Physical examination is remarkable for inflammation at the angle of the mouth, loss of papillae on the tongue, generalized lymphadenopathy, and diffuse hyperpigmentation of the skin. Fecal occult blood test is positive, and ELISA is negative for HIV antibodies. What is the characteristic finding on intestinal biopsy in this patient?
Answer A	Crypt abscesses
Answer A Explanation	Crypt abscesses are characteristic of ulcerative colitis, an inflammatory bowel disease that often manifests with bloody diarrhea, tenesmus, and weight loss.
Answer B	PAS-positive, acid-fast macrophages
Answer B Explanation	PAS-positive, acid-fast macrophages may be present in HIV infections as a result of opportunistic infection caused by Mycobacterium avium intracellulare.
Answer C	PAS-positive, non-acid-fast macrophages
Answer C Explanation	[[AnswerCExp::Whipple disease is characterized by PAS-positive non-acid-fast inclusions in macrophages on duodenal biopsy.]]
Answer D	Diffuse lymphocytic infiltration
Answer D Explanation	Diffuse lymphocytic infiltration is characteristic of intestinal lymphoma.
Answer E	Normal mucosa
Answer E Explanation	Changes in mucosa observed on endoscopy typically include yellow shaggy mucosa with erythematous eroded patches.
Right Answer	C
Explanation	[[Explanation::Whipple disease is a rare systemic infection caused by Tropheryma whipplei, a gram-positive bacillus. The majority of patients with clinical manifestations that include weight loss, diarrhea, malabsorption symptoms, non-deforming arthritis, and generalised lymphadenopathy. Complications of Whipple's disease frequently involve the myocardium and the nervous system. Duodenal biopsy typically demonstrates PAS-positive inclusions in macrophages, however, the most specific test for diagnosis is usually PCR. Educational Objective: Whipple disease is characterized by PAS-positive non-acid-fast inclusions in macrophages on duodenal biopsy. Changes in mucosa observed on endoscopy typically include yellow shaggy mucosa with erythematous eroded patches. References: Fenollar F, Puéchal X, Raoult D. Whipple's disease. N Engl J Med. 2007;356:55-66. First Aid 2015 page 361.]]
Approved	Yes
Keyword	Whipple disease, Macrophages, Duodenal biopsy, Diarrhea, Abdominal pain, Weight loss, Tropheryma whipplei
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