Primary Sclerosing Cholangitis Complicated with Aphthoid Colitis Difficult to Diagnose from IgG4-Related Sclerosing Cholangitis.

A 19-year-old man visited our hospital because of diarrhea and blood and liver dysfunction. Magnetic and endoscopic retrograde cholangiography revealed diffuse narrowing of the common biliary tract and intrahepatic biliary tract. A biopsy specimen from the narrowed area of the common biliary tract revealed IgG4-related sclerosing cholangitis (IgG4-SC). Colonoscopy showed multiple aphthoid colitis. He was treated with corticosteroids, and the levels of hepatobiliary enzymes, IgG, and IgG4 gradually decreased. This is an extremely rare case of colitis in which the patient had a phenotype of sclerosing cholangitis similar to IgG4-SC, which was finally diagnosed as primary sclerosing cholangitis.