A Diagnostic Paradox: Identifying IgG4-Related Disease in a Patient Previously Diagnosed with Sjogren's Syndrome

We present the case of a 77-year-old male with a history of rectal adenocarcinoma and Sjogren's disease who was admitted for severely elevated liver function tests. Cross-sectional imaging demonstrated a dilated bile duct, and eventual biopsy of the area showed fibrosis and lymphocytic infiltrate consistent with IgG4-related disease. The patient was treated with rituximab and a prednisone taper. This case discusses the clinical, laboratory, and imaging hallmarks of this rare disease and illustrates the practical challenges of distinguishing it from other rheumatologic conditions.