Page 423 - Concise Pathology for Exam Preparation ( PDFDrive )

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408 SECTION II Diseases of Organ Systems
Epithelial Defects

• Presence of defects in intestinal epithelial tight junction barrier function (associated with
NOD2 polymorphisms).
• Mutation of the organic cation transporter SLC22A4 in Crohn disease leading to the
defective transepithelial transport.
• Defects in extracellular barrier formed by secreted mucin.
• Abnormality in Paneth cell granules, which contains antibacterial peptides called defen-
sins due to ATG16L1 mutations, is implicated in IBD. It is thought that defective
epithelial anti-microbial function may contribute to the genesis of IBD.

Microbial Factors
Microbes provide an antigenic trigger to a basically dysregulated immune system.

Inflammation
Inflammation is the final common pathway for pathogenesis of IBD. It induces
• Impaired integrity of mucosal–epithelial barrier
• Loss of surface epithelial cell absorptive function

Q. Outline the clinical features and morphology of Crohn disease.

Ans. Crohn disease (also called terminal ileitis, regional enteritis or granulomatous colitis)
is a systemic inflammatory disease, which predominantly affects GIT (mainly terminal
ileum, ileocaecal valve and caecum) and has the following characteristic features:
• Sharply delimited and typically transmural involvement of bowel
• Presence of noncaseating granulomas
• Fissuring with formation of fistulas

Clinical Features

• May affect any age, but major peaks in the second and third decades of life
• Presents with recurrent episodes of diarrhoea, crampy abdominal pain, fever and
melena
• Remissions and relapses are common.
• Patients may develop malabsorption, fistula formation and intestinal stricture or
obstruction. Fistula may form to other loops of bowel, urinary bladder, vagina and
perianal skin.
• Extraintestinal manifestations include uveitis, sacroiliitis, migratory polyarthritis,
erythema nodosum, bile duct inflammatory disorder, obstructive uropathy and
nephrolithiasis.

Gross Morphology
• Serosa is dull and granular with creeping fat appearance.
• Mesentery is thickened, edematous or fibrotic.
• Intestinal wall is rubbery and thick due to oedema and inflammation in the early stages
and fibrosis and hypertrophy of muscularis propria in the later stages.
• Lumen is narrowed (string sign on X-ray).
• Skip lesions are characteristic (sharp demarcation of the involved segment from the
uninvolved).
• Aphthous linear ulcers (cobblestone appearance), fistula or sinus tract formation,
depending on the stage of the disease, may be seen.

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