Which antibody is most specific for primary biliary cirrhosis?

• A. Anti-SMA antibodies
• B. Anti-HBs antibodies
• C. Anti-Nuclear antibodies
• D. Anti-Mitochondrial antibodies

Answer: (D)

Anti-mitochondrial antibodies are the antibody most specific for primary biliary cirrhosis. This autoimmune liver disease targets small intrahepatic bile ducts, and AMA—especially antibodies against the pyruvate dehydrogenase complex within mitochondria (commonly the M2/E2 subunit)—is found in the vast majority of patients with PBC and is highly specific for this condition. In contrast, smooth muscle antibodies are more typical of autoimmune hepatitis, anti-nuclear antibodies can be seen in several autoimmune diseases without being specific to PBC, and anti-HBs antibodies indicate immunity to hepatitis B, not PBC. So the presence of AMA strongly supports a diagnosis of primary biliary cirrhosis.