Autoantibodies associated with primary biliary cholangitis are common among patients with systemic lupus erythematosus even in the absence of elevated liver enzymes.

Knowledge of concomitant autoimmune liver diseases (AILD) is more detailed in primary Sjogren's syndrome (pSS) compared to systemic lupus erythematosus (SLE). Herein, the prevalence of autoantibodies associated with autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) was investigated in stored sera from patients with SLE (n=280) and pSS (n=114). Antibodies against mitochondria (AMA), liver-kidney microsomal (LKM) antigen, smooth muscle (SMA) and antinuclear antibodies (ANA) were analysed with immunofluorescence microscopy. In addition, AILD-associated autoantibodies were tested with immunoblot. Prior to sampling, eight SLE (2.9%) and three pSS (2.6%) cases were diagnosed with AILD. Among SLE-cases without known AILD (n=272), 26 (9.6%) had PBC-associated antibodies, 15 (5.5%) AIH-associated antibodies (excluding ANA), and one serological overlap. Most subjects with PBC-associated autoantibodies had liver enzymes within reference limits (22/27, 81%) or mild laboratory cholestasis (2/27; 7.4%), whereof one fulfilled the diagnostic PBC-criteria. AMA-M2 detected by immunoblot was the commonest PBC-associated autoantibody in SLE (20/272, 7.4%). The prevalence of SMA (4.4%) was comparable with a healthy reference population but associated with elevated liver enzymes in 4/12 (25%), none meeting AIH-criteria. The patient with combined AIH/PBC-serology had liver enzymes within reference limits. Among pSS-cases without known AILD (n=111), 9 (8.1%) had PBC-associated, 12 (10.8%) AIH-associated antibodies and two overlap. PBC-associated antibodies were as frequently found in SLE as in pSS but were, with few exceptions, not associated with laboratory signs of liver disease. Overall, AILD-autoantibodies were predominately detected by immunoblot and no significant difference in liver enzymes was found between AILD-autoantibody negative and positive patients.