When Chest Pain Unmasks the Liver: Acute Pericarditis Leading to the Diagnosis of AIH-PBC Overlap Syndrome.

Autoimmune pericarditis is commonly idiopathic but may represent the initial manifestation of systemic autoimmune disease. Hepatic autoimmune disorders rarely present with primary cardiac involvement, and recognition of extrahepatic presentations is essential for early diagnosis and prevention of organ damage. Autoimmune hepatitis-primary biliary cholangitis (AIH-PBC) overlap syndrome is an uncommon entity characterized by combined hepatocellular and cholestatic immune-mediated injury. A previously healthy young woman presented with progressive pleuritic chest pain and dyspnea and was found to have a large pericardial effusion causing hemodynamic compromise requiring surgical drainage. Pericardial pathology demonstrated acute and chronic fibrinous pericarditis. Initial evaluation revealed elevated inflammatory markers and mild transaminitis with positive autoimmune serologies including antinuclear antibody and anti-smooth muscle antibody. Following clinical improvement, she developed recurrent pericarditis accompanied by worsening liver enzyme abnormalities. Liver biopsy demonstrated chronic active hepatitis with bile duct injury and bridging fibrosis, consistent with autoimmune hepatitis-primary biliary cholangitis overlap syndrome. Cardiac magnetic resonance imaging confirmed active pericardial inflammation without myocarditis. Immunosuppressive therapy with corticosteroids followed by azathioprine resulted in clinical stabilization. This case highlights autoimmune pericarditis as the presenting manifestation of AIH-PBC overlap syndrome and underscores the importance of evaluating unexplained pericarditis for systemic autoimmune disease. Early recognition of cardio-hepatic autoimmune overlap allows timely immunosuppressive therapy and may prevent progression to advanced hepatic fibrosis.