Autoimmune pancreatitis: Cornerstones and future perspectives

Table 1 Differential characteristics between type 1 and type 2 autoimmune pancreatitis

	AIP-1	AIP-2
Gender (M:F)	3:1	1:1
Mean age at disease onset	60-70 yr	40-60 yr
Epidemiology	Asia > Western Countries	Western Countries > Asia
Main clinical manifestations	Painless jaundice (75%); Abdominal symptoms (40%)	Abdominal pain and acute pancreatitis (50%)
	Weight loss
	Diabetes and exocrine pancreatic insufficiency
Extrapancreatic manifestations	IgG4-related disease extrapancreatic manifestations (50%)	IBD (49%-67%)
	Hepatobiliary disease
	Retroperitoneal fibrosis and/or aortitis
	Head and neck involvement
	Mikulicz syndrome
Serum IgG4 levels	Elevated (circulating IgG4 to IgG levels typically > 10%) (50%)	Normal (p-ANCA and c-ANCA autoantibodies often positive)
Histologic features	Lymphoplasmacytic infiltrates rich in IgG4+ plasma cells	Granulocytic epithelial lesions
	Storiform fibrosis
	Obliterative phlebitis
Steroid therapy	Responsive	Responsive
Relapse	High rate (39%)	Rare

AIP: Autoimmune pancreatitis; IBD: Inflammatory bowel disease; ANCA: Anti-neutrophil cytoplasmatic antibodies; IgG: Immunoglobulin G; AIP-1: Type 1 autoimmune pancreatitis; AIP-2: Type 2 autoimmune pancreatitis.

Table 2 Main radiological features of autoimmune pancreatitis

CT scan	Diffuse or focal sausage-like swelling
	Cut-tail sign
	Homogeneous reduced enhancement with dotted contrast enhancements of normal parenchyma
	Hypo-enhanced capsule-like rim with delayed enhancement
	Thickened hyperdense MPD walls
MRI	Diffuse or focal lower intensity signal on T1-weighted MRI images, with an even more hypointense capsule-rim
	Moderately higher intensity signal on T2-weighted images, still with a low-intensity fibrotic rim
	DWI homogeneously hyperintensity
MRCP	Multiple and long MPD skip narrowings
	No upstream dilatation
	Side PD branches (icicle sign)
	Duct-penetrating sign, in case of mass-forming AIP
18F-FDG PET-CT	Diffused or focal increased uptake
EUS	Diffuse pancreatic enlargement, with echopoor echotexture, loss of interface with the splenic vein, concomitant intraparenchymal hyperechoic foci and strands
	Hyperechoic MPD walls
	Solitary, irregular, hypoechoic mass, in case of mass-forming AIP, generally in the head of the pancreas, without upstream dilatation of the MPD
Elastography	Magnified parenchymal stiffness

AIP: Autoimmune pancreatitis; CT: Computed tomography; MPD: Main pancreatic duct; MRI: Magnetic resonance imaging; MRCP: Magnetic resonance cholangiopancreatography; FDG: Fluorodeoxyglucose; PET: Positron emission tomography; EUS: Endoscopic ultrasound.