RC 1701 - IgG4-related disease: what is it and what do I need to know?
IgG4-related disease represents a systemic fibro-inflammatory condition, which includes autoimmune pancreatitis. The condition was first reported in 2003 by Kamisawa and colleagues and during the same year autoimmune pancreatitis was also sub-classified into two histologically separate sub-types, with the “classical” type 1 form comprising part of the IgG4-related disease spectrum. Multiple modality imaging plays a central role in the diagnosis of both pancreatic and extra-pancreatic disease involvement which can affect multiple organs. This session will review the systemic manifestations of IgG4-related disease, including both pancreatic and hepatobiliary findings. In particular, various tips and tricks will be presented, to aid a confident imaging diagnosis in patients with IgG4-related disease.
1. To describe clinical and biological presentation of IgG4-related pancreatitis.
2. To describe morphological and functional (DWI, PET/CT, etc.) imaging features of IgG4-related pancreatitis.
3. To identify imaging findings for the differential diagnosis with other solid pancreatic lesions, i.e. pancreatic cancer, and to avoid unnecessary invasive therapeutic procedures.
The pancreatic manifestation of IgG4-related disease is autoimmune pancreatitis (AIP) which represents a distinct form of chronic pancreatitis. Histologically, AIP is characterised by a dense lymphoplasmacytic infiltrate of mainly CD4+ T lymphocytes and immunoglobulin G4 plasma cells, located around the pancreatic ducts with mass-forming regions of fibrosis. AIP has been classified into focal or diffuse forms. The differential diagnosis between focal AIP and pancreatic adenocarcinoma represents a medical need, since AIP responds to steroid therapy and surgery should be avoided. CT and MRI findings of AIP are characterised by an enlargement of the gland, either focal or diffuse. In CT, the affected areas are isodense before contrast enhancement, hypodense (due to hypovascularity) in the arterial phase with progressive increase in density in the venous and late phases following contrast administration. The involved areas appear hypointense on T1-weighted MR images, mild hyperintense on T2-weighted images with reduced diffusion at DWI. The lesion appears hypovascular during the arterial phase, with progressive enhancement and delayed retention of contrast in the venous and late phases. MRCP is able to assess the involvement of the pancreatic duct system and these features are important in the differential diagnosis with the pancreatic adenocarcinoma in which the main pancreatic duct is characterised by single short stenosis, with marked dilation of the upstream ductal system. In cases in which AIP involves the head of the pancreas, dilatation of the common bile ducts and the intrahepatic ducts can be seen.
1. To describe clinical, biological presentation and morphological and functional imaging findings for the diagnosis of IgG4-related cholangitis.
2. To discuss the role of imaging to avoid unnecessary invasive diagnostic and/or therapeutic procedures.
3. To discuss the diagnostic criteria to differentiate IgG4-related cholangitis from other causes of cholangitis and biliary cancer.
IgG4-related cholangitis is frequent in patient with IgG4-related disease. IgG4-RC should be carefully diagnosed based on a combination of clinical, serological, morphological, and histopathological features. Asian Diagnostic Criteria (Japan-Korea Consensus) and Mayo Clinic Diagnostic Criteria (The HISORt Criteria) have been commonly accepted. On imaging, the affected segments demonstrate irregular stenosis, focal, or diffuse circumferential thickening of the wall with contrast enhancement. The most commonly involved segment are the intrapancreatic segment of the common bile duct showing tapering with upstream biliary dilatation and the biliary convergence. It remains difficult to distinguish IgG4-RC from primary sclerosing cholangitis (PSC) or bile duct malignancy based on imaging features alone. The presence of other organs' involvement, especially pancreatic abnormalities, and elevated serum IgG4 level favour a diagnosis of IgG4-RC. The presence of an inflammatory bowel disease is more frequent in PSC. Biopsy should be used in all patients with a suspicion of malignancy. Although some patients may respond to biliary drainage or surgical resection, IgG4-RC displays a good response to steroid therapy, as is the case for pancreatic lesions. Thus, early introduction of steroid therapy is recommended, especially for patients with obstructive jaundice.
1. To describe extra-pancreatic and extra-biliary manifestation of IgG4-related disease.
2. To describe the imaging findings of the most common extra-pancreatic and extra-biliary organ involvement.
3. To discuss the role of “whole-body” imaging modality for the diagnosis and the follow-up of IgG4-related systemic disease.
IgG4 related diseases include swelling of involved organs, a lymphoplasmacytic infiltrate with IgG4-positive plasma cells and a variable degree of fibrosis. Elevated serum concentrations of IgG4 are found in 60-70 percent of patients. IgG4-RD often affects more than one organ. Immunoglobulin G4-related disease (IgG4-RD) generally occurs most commonly in middle-aged and older men, although disease extent and severity appear to be similar in men and women. IgG4-RD-associated disorders - other than Type 1 AIP and IgG4-related sclerosing cholangitis - include: aalivary and lachrymal gland involvement: dacryoadenitis/sialadenitis and sclerosing sialadenitis: about 40 percent of patients with AIP also have salivary or lachrymal gland involvement (despite marked lachrymal and salivary gland enlargement, these patients experience relatively mild dryness of the eyes and of the mouth than patients with Sjogren’s syndrome); inflammatory orbital pseudotumour: account for 25 to 50 percent of all orbital pseudotumours; idiopathic retroperitoneal fibrosis and mesenteritis, chronic sclerosing aortitis and periaortitis: it involves the infrarenal aorta and simultaneously affect the iliac arteries (chronic inflammatory and fibrotic change can involve regional tissues, such as the ureters, leading to obstructive uropathy); Riedel’s thyroiditis; interstitial pneumonitis and pulmonary inflammatory pseudotumours, which may mimic sarcoidosis; tubulointerstitial nephritis and membranous glomerulonephritis, in most cases with involvement of other organs. The likelihood of IgG4-RD is significantly increased if high serum levels of IgG4, allergic symptoms, and/or other fibrotic processes are also present. Because of the systemic nature of the disease, imaging workup of IgG4-RD should always include whole body examinations to detect multiorgan involvement.