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Malabsorption syndromes (Mucosal abnormalities (Loss of SA (Celiac…

- - - - Lactase deficiency in brush border of enterocytes
        
        Acquired (late childhood)
        
        Congenital (rare; AR)
      - Osmotic diarrhea w/ ↓ stool pH
      - Villi appear normal
        (Except when after viral enteritis, which injures the tips and causes temporary deficiency)
  - - - Immune-mediated villi damage
        • GLIADIN
        
        Gliadin absorbed --> Deamidated by tissue transglutaminase (tTG) --> Presented by MHC II --> Helper T cells mediate tissue damage
        
        :star:HLA-DQ2 & HLA-DQ8
        
        Northern European descent
        (Found worldwide, too)
        
        Infectious:
        • Gliadin homologous to Adenovirus 12 protein
        • A/w high reovirus antibody titers
      - Findings
        
        Microscopic:
        • Intraepithelial lymphocytosis
        • Villous atrophy
        • Crypt hyperplasia
        
        Labs:
        • IgA Anti-tissue transglutaminase (IgA tTG))
        • Anti-endomysial antibody
        • Anti-deamidated gliadin peptide antibodies
        • IgA deficiency
        
        • Failure to thrive
        • Abdominal distension/bloating
        • Diarrhea
        • Dermatitis herpetiformis (IgA deposition)
      - :check:Distal duodenum most involved
      - Sx resolve w/ gluten-free diet
      - Complications:
        • Small bowel carcinoma
        • T cell lymphoma
        • Iron deficiency anemia
    - - • Villous atrophy w/ plasma cells
        :check:• Jejunum & ileum
        ---> Thus megaloblastic anemia from B12 & folate deficiency
      - Tx: Antibiotics
      - Etiology
        • Unknown! Often after infectious diarrhea
        • Tropical regions (e.g., Caribbean)
- - - - Macs partially destroy it -->
        "Foamy" macrophages in intestinal lamina propria
        • PAS(+)
        
        Macs compress lacteals
        --> Chylomicrons can't be transferred to lymphatics
        --> Fat malabsorption & steatorrhea