Clinical clues to suspicion of IgG4‐associated sclerosing cholangitis disguised as primary sclerosing cholangitis or hilar cholangiocarcinoma

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Abstract
This study aimed to determine the clinical characteristics of immunoglobulin G4 (IgG4)-associated sclerosing cholangitis (ISC) and provide clinical clues differentiating ISC from primary sclerosing cholangitis (PSC) or hilar cholangiocarcinoma (CCC). Sixteen patients with ISC manifesting as hilar/intrahepatic strictures were analyzed for clinical characteristics and compared with patients with PSC and hilar CCC as disease controls for histology and serum IgG4 levels. Distinguished biliary imaging findings of ISC included multifocal biliary tree involvement (n = 14), concentric bile duct thickening with preserved luminal patency (n = 13), and relatively mild proximal dilatation, despite prominent bile duct thickening (n = 11). Serum IgG4 levels were elevated in 12 patients (75%), but not in any of the 25 patients with hilar CCC. Ten patients (63%) had a past or concurrent history of autoimmune pancreatitis (AIP). The significant infiltration of IgG4-positive cells was observed with endobiliary or liver biopsy in 11 of 16 patients (69%) with ISC, but not in any patients with PSC or hilar CCC. Extrabiliary organ involvement, including sialadenitis, inflammatory pseudotumor of the liver and kidney, and retroperitoneal fibrosis, was present in seven patients. Marked improvement of biliary strictures and/or extrabiliary involvement was observed in all ISC patients after steroid therapy. ISC should be considered in the differential diagnosis of hilar/intrahepatic biliary strictures. Past or concurrent AIP or extrabiliary organ involvement strongly suggests the possibility of ISC. Significant infiltration of IgG4-positive cells on endobiliary or liver biopsy specimens, and/or elevated serum IgG4 levels, highly support the diagnosis of ISC and provide the rationale for steroid therapy.