Autoimmune Pancreatitis

Fig. 1: Axial CT image of a 61-year-old man with abdominal pain shows mild diffuse enlargement of the pancreas, loss of pancreatic lobulation and minimal peripancreatic fat stranding (arrows).

Fig. 2: An ERCP image (injection of pancreatic duct) shows irregular narrowing of the pancreatic duct (arrowheads).

Facts

• Relatively new, rare disease first described in 1995 by Yoshida et al.
• Chronic pancreatitis characterized by autoimmune inflammatory process (lymphocytic infiltrates) with associated fibrosis of pancreas
• Associated with immunologic abnormalities: hypergammaglobulinemia, elevated serum IgG4 levels and autoantibodies against carbonic anhydrase and lactoferrin
• Pathology shows diffusely indurated and firm pancreas, with periductal lymphocytic and plasma cell infiltrates
• Involvement of the gallbladder, bile ducts, kidney, lung and salivary glands has been described

Clinical

• 5-6% of all patients with chronic pancreatitis
• Men > women, most are > 50 years
• Mostly associated with other autoimmune disease e.g. rheumatoid arthritis, Sjogren's syndrome, inflammatory bowel disease
• Responsive to steroid

Imaging

• On CT, diffuse pancreatic enlargement, enhanced peripheral rim of hypoattenuation "halo", low attenuation "mass" in pancreatic head, homogeneous attenuation and loss of lobularity
• Minimal peripancreatic fat stranding
• Involution of pancreatic tail in long-standing disease
• On ERCP, focal, diffuse or segmental pancreatic ductal narrowing, disappearance of right-angled branches

Reference:

Finkelberg DL, Sahani D, Deshpande V, et al. Autoimmune pancreatitis. N Eng J Med 2006;355:2670-2676.