Primary biliary cirrhosis (PBC) is a chronic disease of the liver. It is cholestatic in nature meaning that the primary injury is to the bile ducts within the liver, leading to impairment of bile flow. The clinical features of PBC result from the combined impacts of the liver injury itself and the secondary effects of reduced bile flow.

PBC is characterised by a very high patient incidence (over 95%) of serum autoantibodies. These antibodies, which are directed at very characteristic self-antigens within the mitochondria and nuclei of cells, are an important diagnostic test for the disease. Damage to the bile duct epithelial cells, which is central to the disease process, is probably caused by autoreactive T-cells rather than being antibody mediated. Targeting the autoimmune response at the heart of PBC represents an attractive approach to treatment in the future.

In up to 50% of patients PBC is clinically silent, only being diagnosed when abnormal liver biochemistry tests are observed at screening or assessment for other conditions. At the other end of the disease spectrum a relatively small proportion of PBC patients have the clinical features of cirrhosis (presence of ascites, loss of muscle mass and risk of variceal bleeding), occasionally presenting for the first time with these features. The remaining group of patients (about 50%) demonstrate the characteristic symptoms of PBC. These include itch (typically feeling like it is deep under the skin and with an unusual pattern of distribution, including the palms of the hands and soles of the feet and the scalp), fatigue and cognitive symptoms (poor memory and concentration). The severity of symptoms such as pruritus and fatigue is not related to the severity of underlying liver disease.