The liver plays a pivotal role not only in the induction of the immune response against pathogens, but also in the maintenance of tolerance against self-molecules, being one of the largest lymphoid organs . It is therefore not surprising that the liver may be targeted by a tissue-specific inflammatory process as observed in primary liver autoimmune diseases, namely autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC). Primary immune diseases of the liver are characterized by peculiar histopathology and progressive courses, while virtually all rheumatologic diseases can affect the liver. A clinically significant liver involvement is rare; conversely, liver enzyme abnormalities may be observed in up to half of rheumatology patients. In most cases, a liver biopsy will only demonstrate minor changes and the biochemical findings can be ascribed to the primary affection, while in a small number of patients with rheumatic diseases an overlap syndrome with a coexisting primary liver disease can be diagnosed. In this setting the liver damage is usually progressive, frequently complicated by cirrhosis and portal hypertension. It should, however, be reminded that the most frequent cause of biochemical liver abnormalities among rheumatic patients is provided by medication-induced hepatotoxicity. This chapter is designed to review the wide spectrum of liver involvement that can be seen in the clinical management of patients with extrahepatic autoimmune diseases, but we are convinced that a preliminary discussion of the incidence and prevalence of PBC, PSC, and AIH is a necessary step to understand and manage rheumatological comorbidities in clinical practice [2, 3]. While autoantibodies have different roles in the three conditions, the histological pattern is quite specific, and liver biopsy is a key point for the diagnosis of difficult cases, albeit not recommended in all patients.
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