Inflammatory bowel disease: Pathology review

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Inflammatory bowel disease: Pathology review

Gastrointestinal system

Peritoneum and peritoneal cavity disorders




Inflammatory bowel disease: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A 32-year-old man comes to the office with complaints of pain in the hip joint and stiffness in the lower back for the past month. The symptoms are worse in the morning and improve with activity and exercise. Review of systems reveals intermittent abdominal pain and frequent episodes of small-volume bloody diarrhea for the last 3 months. He tried over-the-counter analgesics, which helped the joint pain but made the diarrhea worse. He does not have any pain with urination and has not traveled recently. The remainder of his history is noncontributory. Vitals are within normal limits. BMI is 22 kg/m2. Physical examination shows mild tenderness in the hip joints and limited spinal flexion. Laboratory analysis is shown below:

 Laboratory value  Results 
 Complete blood count 
 Hemoglobin  9.8 g/dL 
 Platelet count  460,000/mm3 
 Leukocyte count  8,000/mm3 

Plain radiographs show signs of sacroiliac joint inflammation. Which of the following is the most likely cause of this patient’s joint pain?  


Alex is a 21 year old college student who has a 2 month history of frequent episodes of abdominal pain and bloody diarrhea. Chris is also a 21 year old college student with painful ulcers in the mouth, intermittent abdominal pain, and non-bloody diarrhea that’s been going on for years. In addition, Chris has a history of recurrent kidney stones.

After careful examination, colonoscopy is ordered in both cases. In Alex’s case, there’s circumferential inflammation that’s continuous throughout an entire section of the rectum and colon. On the other hand, in Chris’ case, there are linear patches of damaged colon with normal mucosa in between, and the rectum is not involved.

Alex and Chris both have inflammatory bowel disease or IBD, which is characterized by chronic gastrointestinal tract inflammation due to autoimmune reactions, as well as systemic symptoms like fatigue, fever and unintentional weight loss. IBD typically has its onset before the age of 30. The exact cause is unknown, but there’s definitely a genetic component because it runs in families. Now, there are two types of IBD - Crohn’s disease and ulcerative colitis.

Okay, now let’s look at each specific disease, starting with Crohn’s disease, which is mostly caused by an abnormal Th1 cellular response, and a known risk factor is smoking. In Crohn’s disease, the inflammation can pop up anywhere in the GI tract, from the mouth to the anus, but the rectum is often spared. It tends to be most severe at the terminal ileum.

Gastrointestinal symptoms include crampy abdominal pain, watery diarrhea that may or may not be bloody, and sometimes malabsorption symptoms like malnutrition, steatorrhea, or B12 deficiency. A very frequent finding to keep in mind are aphthous ulcers in the mouth. Some individuals may also present esophageal involvement, with odynophagia and dysphagia.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "First Aid for the USMLE Step 1 2018, 28th Edition" McGraw-Hill Education / Medical (2017)

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