Frequency and significance of antibodies to actin in type 1 autoimmune hepatitis

Antibodies to actin have been proposed as diagnostic markers for type 1 autoimmune hepatitis. Our aims were to determine 1) if testing for antibodies to actin is superior to testing for smooth muscle antibodies (SMA); 2) if these antibodies identify patients with distinctive clinical features; and 3) if the production of antibodies to actin is associated with genetic risk factors for autoimmune hepatitis. Sera from 99 patients with type 1 autoimmune hepatitis were tested. The frequencies of HLA B8, DR3, DR4, and A1-B8-DR3 in patient subsets were compared with those in 80 normal subjects. Seventy-three patients (74%) had antibodies to actin. Antibodies to actin were found more commonly in patients with SMA than in patients without them (86% vs. 7%, P < .0001). Screening only for antibodies to actin and antinuclear antibodies (ANA) failed to establish the diagnosis of autoimmune hepatitis in 5 patients. Patients with antibodies to actin were younger than seronegative patients. They were also more commonly DR3-positive than normal subjects and more frequently B8-positive than patients with non-actin-associated SMA (49% vs. 0%, P = .004). Only patients with antibodies to actin died of liver failure (6% vs. 0%), and 10 of 11 patients requiring liver transplantation were seropositive for these antibodies. Indeed, death and liver transplantation occurred more frequently in these patients than in actin-negative patients with ANA (19% vs. 0%, P = .03). We conclude that routine screening for antibodies to actin may miss patients with type 1 autoimmune hepatitis. Antibodies to actin are associated with HLA B8 and DR3, and they identify patients with a poor prognosis.