Antimitochondrial antibody-negative primary biliary cirrhosis: a subset of primary biliary cirrhosis.

Objective: Antimitochondrial antibodies (AMA) are the hallmark in primary biliary cirrhosis (PBC); nevertheless, it has long been recognized that 5-10% patients with typical features compatible with PBC do not have detectable AMA, and they were referred to as 'AMA-negative PBC'. This study aimed to evaluate whether AMA-negative/positive PBC represents different clinical entities.

Methods: We compared the clinical, laboratory, percentage of regulatory T cells (Tregs) in peripheral blood, liver biopsy features and response to treatment of the two groups of patients. The first group was comprised of 12 patients with 'AMA-negative PBC'. The second was made up of another 12 PBC patients with positive AMA.

Results: Antimitochondrial antibodies-negative/positive patients were remarkably similar in terms of clinical manifestations, liver biochemistries and histological findings. The frequency of anti-nuclear antibodies, anti-smooth-muscle antibody, anti-gp210 and anti-sp100 antibody showed no significant difference between the two groups. A significantly lower mean percentage of CD4+CD25(high) T cells was observed in peripheral blood mononuclear cells of AMA-negative/positive PBC patients compared with that of the 12 control subjects (5.8+/-1.8 and 5.4+/-1.4% vs. 7.6+/-1.7% respectively; P=0.014 and 0.004). However, no difference could be found between AMA-negative and AMA-positive PBC patients (P=0.599). After 1 year treatment with ursodeoxycholic acid, the two groups showed similar response.

Conclusion: Antimitochondrial antibody-negative/positive PBC patients are similar in clinical, laboratory, percentage of Treg in peripheral blood, liver biopsy features and response to treatment. This suggests that AMA-negative PBC may be a variant of AMA-positive PBC rather than a separate clinical entity.