GI Mucosal Immunity & GI Autoimmune Diseases Flashcards
What is mucosa associated lymphoid tissue (MALT)?
MALT is a specialized immune system which protects mucosal surfaces. It consists of a collection of immune cells found in the mucosal linings of the GI.
Describe the 3 components of the mucosal immune system
- Effective barrier: The intestinal epithelium prevents toxins and bacteria from entering the bloodstream. Mucus (surface mucosa) traps microbes, peristalsis prevents bacteria from settling and growing, protective secretory factors (antibodies).
- Innate immune system: Initial response to antigen exposure (neutrophils, macrophages and natural killer cells)
- Adaptive immune system: Specific immunity to antigens (APCs, B and T lymphocytes)
What is the etiology of inflammatory bowel disease
It is a result of genetic predisposition (over 160 genes), environmental triggers (antigens, foreign substances), and abnormal immune response (to bacteria) that leads to chronic and aberrant inflammation.
IBD reflects an imbalance of …
IBD reflects an imbalance of inflammatory response
Hallmark of IBD
Accumulation of excess infiltrating lymphocytes, inappropriate recruitment of inflammatory T cells
What are some common laboratory findings suggesting IBD?
Anemia
B12 deficiency
Increased CRP
Fecal calprotectin
When diagnosing IBD, we want to rule out…
infection
2 types of IBD
- Crohn’s disease
- Ulcerative colitis
Describe Crohn’s disease
Chronic inflammatory disease affecting any segment of the GI tract with transmural involvement (mouth to anus). Only the rectum is spared!
4 main clinical patterns of Crohn’s disease
- Inflammation is contained within sharply delineated areas with intervening areas of normal bowel
- Fistulization (channel formation between bowel loops) and abscesses
- Fibrostenosis (periodic narrowing of lumen due to fibrosis resulting from chronic inflammation)
- Presence of non-caseating granulomas
Symptoms of Crohn’s disease (3)
- Intermittent diarrhea
- Abdominal pain
- GI bleeding
Chronic features of Crohn’s disease (3)
- Strictures
- Fistulas
- Malabsorption
Endoscopic features of Crohn’s disease (7)
- Mucosal erythema (redness) & edema
- Superficial ulcers
- Deep linear ulcers on axis
- Nodularity from skip areas (cobblestoning)
- Bowel wall thickens, lumen narrows
- Edematous mesentery with creeping fat
- Fissures, fistulas, abscesses, adhesions, perforation
Histologic features of Crohn’s disease (8)
- Mucosal inflammation (crypt abscesses)
- Crypt distortion
- Pyloric metaplasia
- Paneth cell metaplasia
- Ulceration
- Transmural inflammation
- Granulomas
- Thickening/fibrosis
Natural history of IBD: Crohn’s disease
- Disease location remains stable over time
- 1/3 of patients develop stricturing or penetrating complications
- Long-term remission is rare
- Can lead to steroid-dependency, hospitalization, surgery and recurrence
Define ulcerative colitis
Chronic inflammatory disease of the colorectum generally restricted to the mucosa. The rectum IS involved.
When ulcerative colitis affects the whole colon, it is called…
pancolitis
What is the main histological distinction between Crohn’s disease and ulcerative colitis?
CD: granulomas
UC: no granulomas
What are the names for ulcerative colitis affecting…
a) rectum and sigmoid colon only
b) rectum, sigmoid and descending colon
c) entire colon
a) procto-sigmoiditis
b) left-sided colitis
c) extensive colitis
Name the types of ulcerative colitis from mild to severe. How do the symptoms progress?
Mild: procto-sigmoiditis
Moderate: left-sided colitis
Severe: extensive colitis
Symptoms go from intermittent bleeding and some constipation to significant bleeding, frequent stools, pain, fevers.
What is the most severe case of ulcerative colitis?
Toxic megacolon
What is toxic megacolon?
When the colon (muscularis propria and neural plexus) is subjected to toxic damage, which disrupts neuromuscular function.
The colon dilates and becomes gangrenous.
Endoscopic features of UC (4)
- Mucosal erythema (redness), granularity, friability
- Broad ulceration
- Regenerating mucosa (pseudopolyps)
- Progressive mucosal atrophy (flattened surface, no mural thickening)
Histologic features of ulcerative colitis (4)
- No granulomas!
- Mononuclear infiltrate
- Crypt abscesses
- Glandular distortion
Tobacco can prevent…
ulcerative colitis
Natural history of UC
- Disease location remains stable over time
- Small risk of colon cancer
Extra-intestinal manifestations of IBD (CHEATS)
C: cholangitis
H: hemotologic
E: eye
A: arthritis
T: thromboembolism
S: skin
Name the 3 genetic factors that are associated with celiac disease
HLA
DQ2
DQ8
(gene loci)
5 types of celiac disease
- classic or typical CD
- atypical celiac sprue
- asymptomatic (silent) CD
- Latent (potential) celiac disease)
- Refractory celiac disease
Which is more common?
a) silent celiac sprue
b) symptomatic celiac sprue
a) silent celiac sprue is 7x more common
Clinical presentation of celiac disease (main symptoms)
- Main age at presentation: 45
- Episodic diarrhea
- Distention
- Steatorrhea
Describe stages zero to four of celiac disease (Marsh classification)
