Early-onset autoimmune hepatitis is associated with a C4A gene deletion.

BACKGROUND: Autoimmune hepatitis is an immunologically mediated disorder with some similarities to systemic lupus erythematosus, including an association with HLA-A1, B8, DR3. This haplotype includes a C4A, 21-OHA gene deletion. Low serum levels of complement and C4 null alleles have been reported in autoimmune hepatitis, but studies have been at the protein level only.

METHODS: Twenty-four white patients with autoimmune hepatitis were studied by Southern blots using a C4A gene complementary DNA probe. HLA A, B, and C typing was determined using standard microcytotoxicity assays, and DR and DQ specificities were determined by restriction fragment length polymorphism analysis.

RESULTS: Thirteen of 24 patients had the C4A gene deletion compared with 12 of 90 controls. HLA-A1 and B8 were increased in patients with autoimmune hepatitis, as were HLA-DR3 (DR17), Dw24, DQ2. Patients with a C4A gene deletion presented at a younger age than those without the deletion and had significantly lower serum C3 and C4 levels. The C4A gene deletion was associated with HLA-A1, B8, DR3 in all but 1 patient who was HLA-DR3 negative.

CONCLUSIONS: A C4A gene deletion is found in patients with autoimmune hepatitis, especially those presenting at a young age. This complement gene deletion may be an important factor in the development of this disease.