Autoimmune Pancreatitis

 

Epidemiology and Etiology:

    • Middle age (range 10s to 70s)
    • may be associated with other autoimmune disorders:
      • Sjogren syndrome
      • PSC
      • PBC
      • IBD
      • SLE
      • DM
      • Retroperitoneal fibrosis

 

Common sites:

    •  

 

Gross features:

    • firm enlargement of the pancreas
      • diffuse, localized, or multifocal
      • may be centered in the head
    • irregular stenosis of the pancreatic ductal system

 

Histologic features:

    • chronic pancreatitis
    • dense duct-centric inflammation (main and medium-sized to large interlobular ducts)
      • lymphocytic or lymphoplasmacytic
        • with or without lymphoid follicle formation
        • T cell predominance (CD4/CD8)
          • not monoclonal (as in lymphoma)
      • May be unevenly distributed
      • May see eosinophils, neutrophils, macrophages, dendritic cells
      • expansion of periductal fibrous tissue containing numerous inflammatory cells
      • acini and islets may be affected
    • reactive or degenerative ductal epithelial changes
    • extensive fibrosis in advanced cases
      • periductal
      • perilobular > intralobular
      • peripancreatic soft tissues
    • periphlebitis often of small to medium sized veins
      • may involve the portal vein
      • may see frank vasculitis
    • interstitial fibroblastic proliferation with storiform architecture (“inflammatory pseudotumour-like”)
    • not normally seen (in contrast to alcoholic):
      • calcification
      • fat necrosis
      • protein plugging
      • psuedocyst formation

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 

 

 

 

Molecular features:

    • DRB1*0405-DQB1*0401 haplotype associated

 

Other features:

    • Overlap with nonalcoholic duct destructive chronic pancreatitis and lymphoplasmacytic sclerosing pancreatitis
    • radiology
      • ERCP – may see segmental or diffuse narrowing of the main pancreatic  duct
        • May see Sclerosing changes of extrapancreatic bile ducts similar to PSC
      • mimics carcinoma with a capsule-like rim
    • bloodwork:
      • autoantibodies (most)
        • ANA
        • Antilactoferrin (ALF)
        • Anticarbonic anhydrase II (ACA-II)
        • Rheumatoid factor
        • Anti-alpha-fodrin
        • RARELY antimitochondrial (M2) (elevated in PBC
        • USUALLY NOT Antineutrophil cytoplasmic autoantibodies (ANCAs)
      • hypergammaglobulinemia (IgG4)
      • eosinophilia
    • complications:
      • diabetes mellitus
      • obstructive jaundice (rarely occurs in other types of pancreatitis
    • considered reversible with steroids (and DM is reversible as well)
      • some patients improve spontaneously with no treatment

 

References:

    • Sternberg 2004
    • Essentials of AP 2006
    • Odze 2004