Autoimmune liver diseases.

The differential diagnosis of the three disorders that are usually classified as autoimmune liver diseases, namely autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC), requires careful exclusion of other causes of chronic liver disease together with the finding of suggestive patterns of abnormalities of serum biochemical parameters, immunoglobulin isotypes and 'conventional' non-organ-specific autoantibodies. Antimitochondrial antibodies (particularly those reacting with epitopes on the E2 components of the pyruvate dehydrogenase and other 2-oxo-acid dehydrogenase complexes), and some sub-specificities of antinuclear antibodies, are virtually pathognomonic of PBC. Anti-liver-kidney microsomal antibodies reacting with defined epitopes on the cytochrome isoform P4502D6 are relatively specific for a small sub-group of (so-called 'type 2') AIH. However, most of the other serological parameters lack specificity. Additionally, within and between each disease group there is wide variability, even among patients with comparable severity of liver damage. Thus, in many cases, liver histology and/orcholangiography is still required for definitive diagnoses or for assessing stage and severity of these disorders. A number of autoantibodies that are more directly related to the liver than the 'conventional' autoantibodies are showing promise as possibly more specific diagnostic markers of AIH. Commercial tests for some of these are under development and it is hoped that they will soon become widely available.