Significance of extractable nuclear antigens in childhood autoimmune liver disease

Antinuclear antibody (ANA) is found in connective tissue disorders and in autoimmune liver disease. While ANA-positive connective tissue disorders are subdivided according to possession of specific antibodies to extractable nuclear antigens (ENA) (anti-ribonucleoprotein (anti-RNP), anti-Smith (anti-Sm), anti-Ro, anti-La), little is known about the presence and significance of ENA in autoimmune liver disease. To investigate this, we have tested 35 children with autoimmune hepatitis (AIH) (19 ANA and/or smooth muscle antibody-positive (ANA/SMA+ve); 16 liver kidney microsomal 1-positive (LKM-1 + ve)) and 14 with ANA/SMA+ve autoimmune sclerosing cholangitis (ASC), using both double dimension immunodiffusion and ELISAs. Eighty children with non-autoimmune liver disease (20 alpha 1-antitrypsin deficiency, 20 Wilson's disease, 20 Alagille's syndrome and 20 chronic hepatitis B virus infection) and 20 healthy controls were also tested. ENA were detected in seven (20%) patients with AIH: two ANA-positive, one SMA-positive and four LKM-1-positive. Three were positive for anti-Sm, two for anti-La, one for anti-Sm/anti-La and one for anti-Sm/anti-La/anti-Ro. ENA-positive had more severe liver disease than ENA-negative patients (P < 0.03). ENA were not detected in ASC, non-autoimmune liver diseases and controls. Our results indicate that ENA reactivity, including anti-Sm and anti-La, characteristic of systemic lupus erythematosus and Sjögren's syndrome, respectively, are present in some patients with AIH even in the absence of ANA, and may characterize a particularly severe form of the disease.