USMLE PRACTICE QUESTION #111
TOPIC: GI Histology/Microbiology
In USMLE practice question #111, we’ll test our ability to diagnose a commonly tested condition based on recognition of the correct histological finding.
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A 27-year-old woman presents to the clinic with chronic diarrhea, fatigue, and unintentional weight loss over the past six months. She describes her stools as bulky, foul-smelling, and difficult to flush. She also notes intermittent abdominal discomfort and bloating after meals. She denies fever, hematochezia, or recent travel. Her medical history is significant for a prior diagnosis of iron deficiency anemia. Physical examination reveals pallor and mild abdominal distention. Laboratory studies show:
Hemoglobin: 9.8 g/dL
Mean corpuscular volume (MCV): 74 fL
Total iron-binding capacity (TIBC): Elevated
Ferritin: Low
Anti-tissue transglutaminase IgA antibodies: Positive
Esophagogastroduodenoscopy is performed, and a biopsy of the duodenum is obtained. Histologic examination reveals a marked reduction in villous height and increased intraepithelial lymphocytosis. Which of the following is most consistent with this patient’s diagnosis?
A) Subepithelial deposits of IgA along the basement membrane
B) Mucosal thickening with noncaseating granulomas
C) Flattening of the mucosa with lamina propria fibrosis
D) Villous atrophy with submucosal eosinophilic infiltrates
E) Blunting of villi with crypt hyperplasia and intraepithelial lymphocytes
Detailed Breakdown of Answers + Correct Answer Below ⏬
ANSWER + QUESTION BREAKDOWN
It’s important to adopt the correct MENTAL MODEL when answering USMLE questions; it saves time and increases accuracy. The mental model outlined below is a foundational component of our test-taking skills masterclass (check it out if you want to elevate your skills). Here’s how to think through this question:
Step 1. Read the last line to get to the heart of the question: “Which of the following is most consistent with this patient’s diagnosis?”
Step 2: Is this a first-, second-, or third-order question?
Answer: 2n order. 1st: Diagnose the condition; 2nd: Identify the corresponding histology.
Step 3: Read the vignette carefully and ask yourself: “What histological finding would support my suspected diagnosis?”
Step 4. Look at the answer choices and select the option most closely resembling your final thought from “Step 3” above.
GENERAL ANALYSIS
This vignette describes a 27-year-old woman with chronic diarrhea, fatigue, unintentional weight loss, and bulky, foul-smelling stools (steatorrhea), which are classic signs of malabsorption. She has a history of iron deficiency anemia, and her physical examination reveals pallor and mild abdominal distention.
ANSWER CHOICES:
CHOICE A: Subepithelial deposits of IgA along the basement membrane
Explanation: This finding is characteristic of dermatitis herpetiformis, a skin manifestation associated with celiac disease. However, this feature is not seen in duodenal biopsies; this finding pertains to skin rather than intestinal biopsies.
CHOICE B: Mucosal thickening with noncaseating granulomas
Explanation: Noncaseating granulomas are characteristic of conditions like Crohn’s disease, which can affect any part of the gastrointestinal tract but does not typically present with villous atrophy or increased intraepithelial lymphocytes. The histologic findings described in this patient (villous atrophy and intraepithelial lymphocytosis) are more consistent with celiac disease than Crohn’s disease.
CHOICE C: Flattening of the mucosa with lamina propria fibrosis
Explanation: Flattening of the mucosa with fibrosis can be seen in conditions like chronic radiation enteritis or ischemic bowel disease.
CHOICE D: Villous atrophy with submucosal eosinophilic infiltrates
Explanation: Decreased extracellular matrix deposition could affect cartilage structure but does not explain the findings in achondroplasia.
CHOICE E: Blunting of villi with crypt hyperplasia and intraepithelial lymphocytes
Explanation: Eosinophilic infiltrates are seen in conditions like eosinophilic gastroenteritis or parasitic infections but are not typical for celiac disease.
FINAL VERDICT…
The patient’s symptoms—chronic diarrhea, weight loss, steatorrhea, iron deficiency anemia—along with positive anti-tissue transglutaminase antibodies and duodenal biopsy findings (villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes), are diagnostic for celiac disease. These histological changes reflect chronic inflammation caused by an autoimmune response to gluten in genetically predisposed individuals.
KEY CONCEPTS:
Celiac disease is an autoimmune disorder triggered by the ingestion of gluten in genetically predisposed individuals. It damages the small intestinal mucosa, particularly the duodenum.
The characteristic histologic findings in celiac disease include:
Villous atrophy
Crypt hyperplasia
Increased intraepithelial lymphocytes (IELs)
These changes impair nutrient absorption, leading to malabsorption syndromes such as iron deficiency anemia and steatorrhea.
CORRECT ANSWER: E) Blunting of villi with crypt hyperplasia and intraepithelial lymphocytes
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