Clinical features of isolated proximal‐type immunoglobulin G4‐related sclerosing cholangitis

<jats:sec><jats:title>Background and Aim</jats:title><jats:p>Immunoglobulin G4‐related sclerosing cholangitis (IgG4‐<jats:styled-content style="fixed-case">SC</jats:styled-content>) presents as isolated proximal‐type sclerosing cholangitis (i‐<jats:styled-content style="fixed-case">SC</jats:styled-content>). The present study sought to clarify the imaging differences between i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> and Klatskin tumor. Differences between i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> and IgG4‐<jats:styled-content style="fixed-case">SC</jats:styled-content> associated with autoimmune pancreatitis (<jats:styled-content style="fixed-case">AIP</jats:styled-content>‐<jats:styled-content style="fixed-case">SC</jats:styled-content>) were also studied.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Differentiating factors between i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> and Klatskin tumor were studied. Serum IgG4 level, <jats:styled-content style="fixed-case">CA</jats:styled-content>19‐9 level, computed tomography (<jats:styled-content style="fixed-case">CT</jats:styled-content>) findings, cholangiography findings (symmetrical smooth long stricture extending into the upper bile duct [<jats:styled-content style="fixed-case">SSLS</jats:styled-content>]), endosonographic features (continuous symmetrical mucosal lesion to the hilar part [<jats:styled-content style="fixed-case">CSML</jats:styled-content>]), endoscopic biopsy results, treatment, relapse, and survival were also compared between patients with i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> and those with <jats:styled-content style="fixed-case">AIP</jats:styled-content>‐<jats:styled-content style="fixed-case">SC</jats:styled-content>.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>For a differential diagnosis between i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> (<jats:italic>N</jats:italic> = 9) and Klatskin tumor (<jats:italic>N</jats:italic> = 47), the cut‐off value of serum IgG4 level was 150 mg/dL (sensitivity, 0.857, specificity, 0.966). Logistic regression analysis indicated that serum IgG4 level, presence of <jats:styled-content style="fixed-case">SSLS</jats:styled-content>, presence of <jats:styled-content style="fixed-case">CSML</jats:styled-content>, and presence of swollen ampulla are independent factor for identifying i‐<jats:styled-content style="fixed-case">SC</jats:styled-content>. Relapse rate was significantly higher in the IgG4‐<jats:styled-content style="fixed-case">SC</jats:styled-content> with <jats:styled-content style="fixed-case">AIP</jats:styled-content> group than in the i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> group (log rank, <jats:italic>P </jats:italic>=<jats:italic> </jats:italic>0.046).</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>Isolated proximal‐type sclerosing cholangitis presents as a nodular lesion with <jats:styled-content style="fixed-case">SSLS</jats:styled-content> and/or <jats:styled-content style="fixed-case">CSML</jats:styled-content> mimicking a Klatskin tumor. Those endoscopic features might provide a diagnostic clue for i‐<jats:styled-content style="fixed-case">SC</jats:styled-content>. i‐<jats:styled-content style="fixed-case">SC</jats:styled-content> is likely to have a more favorable prognosis than IgG4‐<jats:styled-content style="fixed-case">SC</jats:styled-content> with <jats:styled-content style="fixed-case">AIP</jats:styled-content>.</jats:p></jats:sec>