Primary biliary cholangitis (PBC)
Primary biliary cholangitis (PBC) is the most common autoimmune liver disease. In comparison to the other autoimmune liver diseases its course is mild and in many cases restrictions of the liver function only arise after decades without treatment. The former name “Primary biliary cirrhosis” is misleading, since the disease is usually diagnosed when no severe liver damage has yet occured. Usually treatment may then prevent from a severe course of disease and the majority of patients never reach the stage cirrhosis.
At the time of diagnosis, the patient has usually been suffering from primary biliary cholangitis for several years without any noticeable symptoms.
Symptoms of PBC may be:
- dry eyes, dry mouth (sicca syndrome)
- small fat depots near the eyes (Xanthelasma)
- mild joint pain without joint inflammation (Arthralgias)
Only in very few cases the disease really causes liver cirrhosis and the respective symptoms. About 20 % of the patients suffering from PBC also fulfill criteria of autoimmune hepatitis (also called overlap syndrome PBC/AIH). This means that symptoms of both diseases occur together and both diseases have to be treated.
Due to the very slow course PBC is often detected in routine examinations. As in other liver diseases only the synopsis of symptoms, laboratory values and the result of the tissue sample leads to the diagnosis.
- elevated liver enzymes, especially elevated levels of the cholestatic enzymes (AP, -GT)
- only slightly elevated values of GPT and GOT
- elevated level of the gamma globuline IgM
- presence of antimitochondrial antibodies (AMA) in more than 95 % of all cases
The proof of AMA auto antibodies is of great importance for the diagnosis of primary biliary cirrhosis. Almost all patients suffering from PBC show AMA, and nearly all patients showing AMA suffer from PBC. The typical AMA for PBC react specifically with defined molecules, the E2 subunits of the pyruvate dehydrogenase complex PDH-E2. These antibodies can be demonstrated, special laboratory tests exist. If AMA in combination with this specific reaction against PDH-E2 is found, the diagnosis of PBC can be regarded as confirmed. Elevated liver enzymes and PBC specific AMA are commonly regarded as proof of the diagnosis PBC.
Liver histology (tissue examination) shows an inflammation and destruction of the small and medium-sized bile ducts. A liver biopsy is helpful in order to confirm the diagnosis and to assess the stage of the disease, but contrary to autoimmune hepatitis a liver biopsy is not always necessary to make a diagnosis.
In most cases, the course of primary biliary cholangitis is benign. In order to prevent the progression of the disease or in order to slow it down medication with UDCA (ursodeoxycholic acid) is the standard treatment (13-15 mg/kg/day). Treatment should be permanent. Laboratory values improve significantly in most patients under UDCA treatment, which is a good prognostic sign. If, however, laboratory values do not improve significantly under UDCA treatment, it is very likely an aggressive form of the disease, which may also be called secondary autoimmune hepatitis or overlap syndrome. This can also be recognized in a tissue sample (liver biopsy). These patients should be given immunosuppressive drugs in addition to UDCA just like patients suffering from autoimmune hepatitis. However, in most cases a lower dosage of the immunosuppressive drugs seems to be sufficient for these patients.