Erdheim-Chester disease associated with an aggressive form of sclerosing cholangitis

Background Erdheim-Chester disease (ECD) is a rare histiocytic disorder recently recognized as a neoplasm due to the discovery of activating MAPK pathway mutations. Hepatic involvement by ECD is extremely rare. Case presentation We describe a case of a 64-year-old male who presented with pruritis, weight loss, and cholestatic liver function tests. Magnetic resonance imaging of the abdomen showed beaded appearance of the intrahepatic biliary tree. A liver biopsy was suggestive of primary or secondary sclerosing cholangitis. Computerized tomography (CT) of the abdomen showed perinephric and periaortic soft tissue stranding suggestive of ECD. 18 F-fluorodeoxyglucose positron emission/computerized tomography scan showed a mediastinal hilar mass which turned out to be follicular lymphoma. Histopathology of molluscum-like skin lesions showed CD68 + , Factor XIIIa + , and CD1a-foamy histiocytes with multiple giant cells suggestive of ECD. The patient developed recurrent episodes of ascending cholangitis and his hyperbilirubinemia continued to worsen despite stenting of a common hepatic duct stricture found on endoscopic retrograde cholangiopancreatography. Conclusions The absence of associated inflammatory bowel disease and anti-neutrophil cytoplasmic antibody, as well as the rapidity of disease progression, makes us consider the possibility of hepatic involvement by ECD or an overlap syndrome. We want to highlight that negative histopathology should not delay the diagnosis of ECD as effective and potentially lifesaving therapies with BRAF or MEK pathway inhibitors are now available for these patients.